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JAMB PhysicsStudy notes & practice

Use physical ideas and worked calculations to understand motion, waves, electricity and modern technology.

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Foundation revision notes and original practice. These notes cover major physical ideas and selected calculations. More diagrams, experimental data and multi-step problems are still needed.

What these revision notes cover
  • These notes cover major physical ideas and selected calculations. More diagrams, experimental data and multi-step problems are still needed.
  • Written examples do not replace supervised practical instruction.

01 Mechanics

Measurements, units and uncertainty

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What you should be able to do

  • Choose units and measuring instruments
  • Use dimensions, significant figures and uncertainty

Understand it

SI base quantities include length, mass, time, electric current, temperature, amount of substance and luminous intensity. Their units are metre, kilogram, second, ampere, kelvin, mole and candela. Charge is derived from current and time, rather than being an SI base quantity.

Choose an instrument suited to the measurement: a micrometer for small thicknesses, a measuring cylinder for liquid volume, and a balance for mass. Check zero error, read scales carefully and avoid parallax. Precision concerns repeatability; accuracy concerns agreement with the accepted value.

Derived units combine base units: force is kg m s⁻² and pressure is kg m⁻¹ s⁻². Dimensional consistency can reveal an impossible equation but cannot prove the numerical coefficient is right. Quote results to a precision justified by the measurement.

Work through an example

A length is 5.0 cm with absolute uncertainty 0.1 cm. Find percentage uncertainty.

Explanation: (0.1/5.0)×100=2%.

Watch out: Mass is measured in kilograms; weight is a force measured in newtons.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

The SI unit of force is

  1. Newton
  2. Pascal
  3. Watt
  4. Joule
Show answer and explanation

Answer A: Newton

Force is measured in newtons. From F = ma, its SI base-unit expression is kg × m s⁻² = kg m s⁻². A joule measures energy, a pascal measures pressure and a watt measures power; these units describe different quantities.

Question 2

Which is an SI base quantity?

  1. Pressure
  2. Electric current
  3. Energy
  4. Electric charge
Show answer and explanation

Answer B: Electric current

Electric current is an SI base quantity, measured in amperes. Charge is derived from current × time and is measured in coulombs. Pressure and energy also have derived units. Distinguish the physical quantity (current) from the name of its unit (ampere).

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02 Mechanics

Scalars, vectors and position

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What you should be able to do

  • Distinguish distance and displacement
  • Resolve and combine vectors

Understand it

A scalar has magnitude only; a vector has magnitude and direction. Distance is total path length, while displacement is the change in position from start to finish. A round trip can have positive distance and zero displacement.

Resolve a vector of magnitude F at angle θ above the horizontal into Fx=F cosθ and Fy=F sinθ. Add components separately, then use Pythagoras and an angle relation to recover the resultant.

Velocity is measured relative to a frame of reference. Relative velocity of A with respect to B is vA−vB, including signs or directions. Opposite directions must not be treated as if both velocities had the same sign.

Work through an example

A student walks 3 m east and 4 m north. Find displacement magnitude.

Explanation: The perpendicular components give √(3²+4²)=5 m, towards the northeast. Distance walked is 7 m.

Watch out: Distance and displacement magnitude need not be equal.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Which quantity is a vector?

  1. Temperature
  2. Velocity
  3. Energy
  4. Mass
Show answer and explanation

Answer B: Velocity

Velocity specifies both rate and direction of displacement.

Question 2

A runner completes a 400 m lap and returns to the start. Displacement is

  1. 200 m
  2. 400 m
  3. 0 m
  4. 800 m
Show answer and explanation

Answer C: 0 m

Initial and final positions are the same.

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03 Mechanics

Linear motion and motion graphs

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What you should be able to do

  • Apply constant-acceleration equations
  • Read velocity-time and distance-time graphs

Understand it

Speed is distance per time; velocity is displacement per time; acceleration is change in velocity per time. Constant speed does not guarantee constant velocity if direction changes.

For constant acceleration, v=u+at, s=ut+½at² and v²=u²+2as. Choose a positive direction before substituting signed values. These equations do not generally apply unchanged when acceleration varies.

The gradient of a displacement-time graph is velocity; the gradient of a velocity-time graph is acceleration. Area under a velocity-time graph is displacement, with negative areas counted negatively. Under uniform gravity without air resistance, vertical acceleration remains downward throughout flight.

Work through an example

A body starts from rest and accelerates at 3 m s⁻² for 4 s. Find distance.

Explanation: s=0+½×3×4²=24 m.

Watch out: At the highest point of a vertical throw, velocity is zero but acceleration is still downward.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A velocity-time graph with constant positive slope shows

  1. Constant velocity
  2. Constant speed with changing direction only
  3. Decreasing acceleration
  4. Constant acceleration
Show answer and explanation

Answer D: Constant acceleration

Its slope equals acceleration.

Question 2

An object continues in the same direction along a straight line as its speed changes from 2 to 10 m s⁻¹ in 4 s. What is its average acceleration, in m s⁻²?

  1. 8 m s⁻²
  2. 3 m s⁻²
  3. 12 m s⁻²
  4. 2 m s⁻²
Show answer and explanation

Answer D: 2 m s⁻²

a=(10−2)/4=2 m s⁻².

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04 Mechanics

Newton’s laws, momentum and impulse

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What you should be able to do

  • Relate resultant force to acceleration
  • Use momentum conservation and impulse

Understand it

Newton’s first law describes constant velocity when resultant force is zero. The second law relates resultant force to rate of change of momentum and gives F=ma for constant mass. The third law describes equal and opposite interaction forces acting on different bodies.

Momentum is p=mv. Impulse equals change in momentum and, for constant force, Ft. The area under a force-time graph gives impulse even when force varies.

Total momentum is conserved for an isolated system with no net external impulse. In a collision, kinetic energy may change into other forms even though momentum is conserved. Use signed velocities to represent opposite directions.

Work through an example

A 2 kg body changes velocity from 3 to 7 m s⁻¹ in the same direction. Find impulse.

Explanation: Δp=m(v−u)=2(7−3)=8 N s.

Watch out: Action and reaction forces do not cancel on one body because they act on different bodies.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A net force of 12 N acts on 3 kg. Acceleration, in m s⁻², is

  1. 4
  2. 9
  3. 36
  4. 3
Show answer and explanation

Answer A: 4

a=F/m=12/3=4 m s⁻².

Question 2

The area under a force-time graph represents

  1. Distance
  2. Pressure
  3. Impulse
  4. Power
Show answer and explanation

Answer C: Impulse

Its units are N s, equal to momentum change.

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05 Mechanics

Projectiles and circular motion

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What you should be able to do

  • Separate horizontal and vertical projectile motion
  • Explain centripetal acceleration

Understand it

An ideal projectile has constant horizontal velocity and constant downward vertical acceleration when air resistance is neglected. Split initial velocity into horizontal and vertical components before applying the motion equations.

For launch and landing at the same height, time of flight is 2u sinθ/g and range is u² sin2θ/g. Different landing heights require solving the vertical motion instead. The maximum height above launch is u²sin²θ/(2g).

Uniform circular motion has constant speed but changing velocity. Centripetal acceleration v²/r points towards the centre and requires resultant inward force mv²/r. Centripetal describes the role of a force, which may be provided by tension, gravity or friction.

Work through an example

A body moves at 4 m s⁻¹ in a circle of radius 2 m. Find centripetal acceleration.

Explanation: a=v²/r=16/2=8 m s⁻² towards the centre.

Watch out: A projectile’s horizontal velocity is constant only under the stated ideal assumptions.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

At the top of an ideal projectile path, vertical acceleration is

  1. Upward g
  2. Zero
  3. Downward g
  4. Equal to horizontal speed
Show answer and explanation

Answer C: Downward g

Gravity continues to act downward.

Question 2

For fixed speed, doubling a circular path’s radius makes centripetal acceleration

  1. Double
  2. Unchanged
  3. Four times
  4. Half
Show answer and explanation

Answer D: Half

a=v²/r is inversely proportional to radius.

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06 Mechanics

Oscillations and simple harmonic motion

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What you should be able to do

  • Relate period and frequency
  • Explain restoring force, energy and resonance

Understand it

In simple harmonic motion, acceleration is proportional to displacement from equilibrium and directed back towards it: a=−ω²x. The amplitude is the maximum displacement, period is time for one cycle, and frequency is cycles per second.

Frequency f=1/T and angular frequency ω=2πf. In an ideal oscillator, kinetic energy is greatest at equilibrium and potential energy is greatest at the extremes. Total mechanical energy stays constant without damping.

A mass-spring system has T=2π√(m/k); a simple pendulum at small angles has T=2π√(L/g). Forced vibration occurs under a repeating external drive. Resonance gives a large response when the driving frequency is near a natural frequency, limited in practice by damping.

Work through an example

An oscillator completes 20 cycles in 10 s. Find frequency and period.

Explanation: f=20/10=2 Hz, so T=1/2=0.5 s.

Watch out: At an extreme of SHM, speed is zero but restoring acceleration is largest in magnitude.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

In ideal SHM, maximum speed occurs at

  1. An extreme
  2. Three-quarters of the amplitude
  3. Halfway between equilibrium and an extreme
  4. Equilibrium
Show answer and explanation

Answer D: Equilibrium

Potential energy is least and kinetic energy greatest at equilibrium.

Question 2

Doubling pendulum length changes its small-angle period by a factor of

  1. 1/2
  2. √2
  3. 4
  4. 2
Show answer and explanation

Answer B: √2

T is proportional to √L.

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07 Mechanics

Gravitation, weight and orbits

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What you should be able to do

  • Apply inverse-square gravitation
  • Distinguish mass, weight and apparent weightlessness

Understand it

Newton’s law gives gravitational attraction F=GMm/r², where r is distance between centres for spherical bodies. Gravitational field strength near a spherical body is g=GM/r². Mass is an intrinsic measure in kilograms; weight is gravitational force mg.

Gravitational potential relative to infinity is −GM/r. Work against gravity increases potential energy. The escape speed from a spherical body is √(2GM/R) when air resistance and other bodies are neglected.

An orbiting satellite is in continuing free fall, with gravity providing centripetal acceleration. Astronauts feel apparent weightlessness because they and their surroundings fall together, not because gravity has disappeared. A geostationary orbit must meet period, direction and equatorial-plane conditions.

Work through an example

What happens to gravitational force if separation doubles?

Explanation: The inverse-square law gives Fnew=F/2²=F/4.

Watch out: Orbiting close to Earth does not mean gravitational field strength is zero.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A 5 kg mass where g=10 m s⁻² has weight

  1. 50 N
  2. 500 N
  3. 0.5 N
  4. 5 N
Show answer and explanation

Answer A: 50 N

W=mg=5×10=50 N.

Question 2

Apparent weightlessness in orbit occurs mainly because

  1. Air provides all the support
  2. Mass becomes zero
  3. There is no gravity
  4. Everything is in free fall
Show answer and explanation

Answer D: Everything is in free fall

The spacecraft and its occupants accelerate together under gravity.

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08 Mechanics

Equilibrium, moments and stability

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What you should be able to do

  • Apply force and moment balance
  • Relate centre of gravity to stability

Understand it

For a body in static equilibrium, resultant force and resultant turning effect must both be zero. Resolve forces into perpendicular directions and balance each component. An equilibrant is equal and opposite to the resultant of other forces.

Moment equals force times perpendicular distance from the pivot to the force’s line of action. Clockwise and anticlockwise moments balance in equilibrium. A couple consists of equal opposite parallel forces with separate lines of action and creates a turning effect.

A lower centre of gravity and a wider base generally improve stability. Stable equilibrium produces a restoring tendency after a small displacement; unstable equilibrium moves farther away; neutral equilibrium leaves the height of the centre of gravity unchanged.

Work through an example

A 10 N force has a perpendicular distance of 0.4 m from a pivot. A second force has a perpendicular distance of 0.2 m and produces an opposing moment. What magnitude of the second force balances the moments?

Explanation: Balance the opposing moments: 10×0.4=F×0.2, so F=20 N. Each distance is measured perpendicular to the force’s line of action.

Watch out: Use perpendicular distance, not any convenient length on the diagram.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A moment has SI unit

  1. N m
  2. N/m
  3. kg/m³
  4. J/s
Show answer and explanation

Answer A: N m

Moment is force multiplied by perpendicular distance.

Question 2

A wider base generally makes an object

  1. Lower in mass necessarily
  2. More stable
  3. Higher in centre of gravity necessarily
  4. Less stable
Show answer and explanation

Answer B: More stable

The centre-of-gravity line can move farther before falling outside the base.

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09 Mechanics

Friction, viscosity and terminal speed

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What you should be able to do

  • Explain limiting friction
  • Relate fluid drag to terminal motion

Understand it

Friction opposes relative sliding or the tendency to slide at a contact. Static friction adjusts up to a limiting value; in the simple model, limiting friction is μR, where R is the normal reaction. Sliding friction need not equal this maximum static value.

Friction provides grip for walking and braking but also causes wear and heating. Lubrication, smooth bearings and suitable materials reduce unwanted friction. The normal reaction is not always equal to weight, especially on slopes or with additional forces.

Viscosity measures resistance to fluid flow. For a small sphere moving slowly through a viscous fluid under appropriate conditions, Stokes’ drag is 6πηrv. Terminal speed occurs when weight is balanced by upthrust and drag, leaving zero resultant force.

Work through an example

If μ=0.3 and normal reaction is 40 N, find limiting friction.

Explanation: Flim=μR=0.3×40=12 N.

Watch out: Zero resultant force means zero acceleration, not necessarily zero velocity.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

At terminal speed, a falling object’s acceleration is

  1. Downward 2g
  2. Downward g
  3. Zero
  4. Upward g
Show answer and explanation

Answer C: Zero

The opposing forces balance the weight.

Question 2

Lubrication mainly reduces

  1. All pressure
  2. Mass
  3. Gravity everywhere
  4. Unwanted friction
Show answer and explanation

Answer D: Unwanted friction

A lubricant reduces direct contact and resistance between surfaces.

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10 Mechanics

Work, energy, power and energy resources

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What you should be able to do

  • Calculate work and power
  • Trace energy conversions and resource impacts

Understand it

Work done by a constant force is Fs cosθ, where θ is the angle between force and displacement. Kinetic energy is ½mv²; near Earth, gravitational potential-energy change is mgΔh. The area under a force-displacement graph gives work.

Power is the rate of doing work or transferring energy: P=E/t. Energy is conserved overall, although useful mechanical or electrical energy can become less useful dispersed thermal energy. Efficiency is useful output divided by total input.

Hydroelectric systems convert water’s gravitational energy through turbines to electricity; solar cells convert light to electrical energy. Wind, solar and flowing water are renewable resources, while fossil fuels are finite. Every energy system has environmental and practical costs that must be compared.

Work through an example

A machine transfers 600 J in 3 s. Find power.

Explanation: P=600/3=200 W.

Watch out: A device does not create energy; it converts energy between forms.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A 2 kg body moving at 3 m s⁻¹ has kinetic energy

  1. 18 J
  2. 3 J
  3. 9 J
  4. 6 J
Show answer and explanation

Answer C: 9 J

E=½×2×3²=9 J.

Question 2

Which is a renewable energy source?

  1. Petroleum
  2. Natural gas
  3. Coal
  4. Wind
Show answer and explanation

Answer D: Wind

Wind is replenished by atmospheric processes.

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11 Mechanics

Simple machines and efficiency

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What you should be able to do

  • Calculate mechanical advantage and velocity ratio
  • Explain why machines trade force for distance

Understand it

A simple machine changes the size or direction of an applied force. Examples include levers, pulleys, inclined planes, screws and wheel-and-axle systems. A machine can make a task easier without reducing the total energy required below the useful output.

Mechanical advantage is load divided by effort. Velocity ratio is distance moved by effort divided by distance moved by load. Efficiency=(MA/VR)×100%, using consistent definitions.

Real machines lose useful energy through friction and deformation, so efficiency is below 100%. A large mechanical advantage usually means the effort moves through a greater distance than the load. An ideal machine conserves input and output work.

Work through an example

A machine has MA=3 and VR=4. Find efficiency.

Explanation: Efficiency=(3/4)×100%=75%.

Watch out: Mechanical advantage and efficiency are not the same quantity.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A load of 100 N is raised by effort 25 N. MA is

  1. 75
  2. 4
  3. 125
  4. 0.25
Show answer and explanation

Answer B: 4

MA=load/effort=100/25=4.

Question 2

An ideal machine with VR=5 has MA

  1. 5
  2. 10
  3. 2.5
  4. 1
Show answer and explanation

Answer A: 5

At 100% efficiency, MA=VR.

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12 Mechanics

Elasticity and stored energy

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What you should be able to do

  • Apply Hooke’s law within its range
  • Relate stress, strain and Young’s modulus

Understand it

An elastic material returns towards its original shape after deforming force is removed, provided its elastic limit is not exceeded. Hooke’s law states that force is proportional to extension within the proportional region: F=kx.

The elastic potential energy stored by a Hookean spring is ½kx², equal to the area under its force-extension graph. The spring constant k measures stiffness and has unit N m⁻¹.

Stress is force divided by cross-sectional area and strain is extension divided by original length. Young’s modulus is stress/strain in the linear elastic region. Yield and breaking points mark different stages of deformation and should not be confused with the proportional limit.

Work through an example

A spring of constant 200 N m⁻¹ extends by 0.03 m. Find force.

Explanation: F=kx=200×0.03=6 N.

Watch out: Extension is the increase in length, not the final total length.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

The SI unit of Young’s modulus is

  1. Pascal
  2. Coulomb
  3. Second
  4. Metre
Show answer and explanation

Answer A: Pascal

Strain is dimensionless, so the modulus has the unit of stress: Pa.

Question 2

Doubling a Hookean spring’s extension multiplies stored energy by

  1. 4
  2. 1
  3. 2
  4. 1/2
Show answer and explanation

Answer A: 4

Energy is proportional to x².

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13 Fluids

Pressure, density and floating bodies

Read this lesson

What you should be able to do

  • Apply pressure relationships
  • Use Archimedes’ principle and flotation

Understand it

Pressure is normal force per area. Fluid pressure increases with depth according to ΔP=ρgh for a fluid of constant density. Atmospheric pressure contributes to absolute pressure; a gauge may measure only the difference from it.

Pascal’s principle states that a pressure change in a confined fluid is transmitted throughout the fluid. Hydraulic systems exploit equal pressure acting over different piston areas. Barometers measure atmospheric pressure and manometers compare pressures.

Density is mass per volume; relative density compares with a reference and has no unit. Upthrust equals the weight of displaced fluid. A floating body displaces its own weight of fluid, even when its material is denser than water but its average density is lower.

Work through an example

Find the water-pressure increase at depth 2 m using ρ=1000 kg m⁻³ and g=10 m s⁻².

Explanation: ΔP=1000×10×2=20,000 Pa.

Watch out: Upthrust equals the weight of displaced fluid. It equals the body’s weight when the body floats at rest under only weight and upthrust. A supported or suspended submerged body can be balanced by other forces too.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Pressure increases when the same force acts over

  1. The same area
  2. A smaller area
  3. A larger area
  4. An area increased in the same ratio as pressure
Show answer and explanation

Answer B: A smaller area

P=F/A, so reducing area raises pressure.

Question 2

A body floats freely at rest under only its weight and upthrust. Its upthrust is

  1. Less than its weight
  2. Zero
  3. Equal to its weight
  4. Greater than its weight
Show answer and explanation

Answer C: Equal to its weight

Vertical forces balance while it floats at rest.

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14 Thermal physics

Temperature, heat capacity and latent heat

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What you should be able to do

  • Distinguish temperature and thermal energy transfer
  • Calculate sensible and latent heating

Understand it

Temperature describes thermal state and determines heat-flow direction; heat is energy transferred because of a temperature difference. Thermometers use properties that vary predictably with temperature. Kelvin temperature equals Celsius temperature plus 273.15.

For heating without a phase change, Q=mcΔT. Specific heat capacity is energy per unit mass per unit temperature rise; heat capacity applies to the whole object. In an insulated mixing calculation, energy lost by hotter parts equals energy gained by colder parts.

During a phase change at constant pressure, energy can change intermolecular arrangements without raising temperature. Q=mL uses specific latent heat. Evaporation occurs at a surface over a range of temperatures, while boiling occurs throughout a liquid when its vapour pressure matches external pressure.

Work through an example

How much heat raises 2 kg of a substance of c=500 J kg⁻¹ K⁻¹ by 3 K?

Explanation: Q=mcΔT=2×500×3=3000 J.

Watch out: A temperature change of 1°C has the same size as a change of 1 K.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

During melting at constant pressure, supplied energy mainly

  1. Stops molecular motion
  2. Raises temperature continuously
  3. Changes the phase
  4. Destroys mass
Show answer and explanation

Answer C: Changes the phase

Latent heat changes the structure while temperature can remain constant.

Question 2

27°C is approximately

  1. 273 K
  2. 300 K
  3. 27 K
  4. 246 K
Show answer and explanation

Answer B: 300 K

27+273≈300 K.

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15 Thermal physics

Expansion, gases and atmospheric vapour

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What you should be able to do

  • Apply thermal expansion and gas laws
  • Explain saturation and relative humidity

Understand it

For a small temperature change, linear expansion is ΔL=αLΔT. In an isotropic solid, area and volume expansivities are approximately 2α and 3α. A liquid’s apparent expansion depends on expansion of its container as well as the liquid itself.

For a fixed amount of ideal gas, PV/T is constant. Use kelvin and consistent pressure-volume units. Real gases depart from the ideal model because particles have volume and attract one another. Water is unusual because its density is greatest near 4°C at ordinary pressure.

Saturated vapour is in dynamic equilibrium with its liquid at a stated temperature. Relative humidity compares actual water-vapour pressure with saturation vapour pressure at that temperature. Cooling air to its dew point can produce condensation, contributing to dew, mist or cloud.

Work through an example

A gas has volume 2 dm³ at 300 K and constant pressure. Find volume at 450 K.

Explanation: V₂=V₁T₂/T₁=2×450/300=3 dm³.

Watch out: Relative humidity can change when temperature changes even without adding water vapour.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A metal rail is given expansion gaps mainly because it

  1. Expands when heated
  2. Has zero elasticity
  3. Loses all mass in sunlight
  4. Becomes a gas daily
Show answer and explanation

Answer A: Expands when heated

The gaps accommodate thermal length changes.

Question 2

At the dew point, air begins to

  1. Become a vacuum
  2. Lose all nitrogen
  3. Boil
  4. Condense water vapour when further cooled
Show answer and explanation

Answer D: Condense water vapour when further cooled

It has reached saturation for its existing water-vapour content.

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16 Thermal physics

Molecular behaviour and heat transfer

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What you should be able to do

  • Use kinetic ideas for diffusion and surface effects
  • Compare conduction, convection and radiation

Understand it

Brownian motion is irregular movement of small suspended particles caused by molecular impacts. Diffusion reflects net spreading down concentration gradients. Cohesion acts between similar molecules, while adhesion acts between different materials and helps explain wetting and capillary effects.

Conduction transfers thermal energy through interactions within matter without bulk movement. Convection transfers energy through bulk fluid motion. Radiation uses electromagnetic waves and can cross a vacuum.

Thermal conduction rate depends on conductivity, area and temperature gradient. Dark, dull surfaces generally absorb and emit thermal radiation better than shiny surfaces under comparable conditions. A vacuum flask reduces conduction and convection through its vacuum and limits radiation with reflective surfaces.

Work through an example

Why can sunlight warm Earth across space?

Explanation: Radiation transfers energy through the vacuum between the Sun and Earth; no material medium is required.

Watch out: Heat and temperature are not interchangeable quantities.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Which transfer process requires bulk fluid motion?

  1. Radiation
  2. Convection
  3. Conduction
  4. Reflection
Show answer and explanation

Answer B: Convection

Warm fluid moves and carries energy to another region.

Question 2

A vacuum between flask walls mainly suppresses

  1. All radiation completely
  2. Conduction and convection
  3. Evaporation inside all liquids
  4. Gravity
Show answer and explanation

Answer B: Conduction and convection

Removing matter greatly reduces those two transfer mechanisms.

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17 Waves

Waves and their properties

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What you should be able to do

  • Relate wavelength, frequency and wave speed
  • Explain interference, diffraction and polarisation

Understand it

A wave transfers energy without carrying the medium bodily over the full distance. In transverse waves, oscillation is perpendicular to propagation; in longitudinal waves it is parallel. Mechanical waves need a medium, while electromagnetic waves can travel in a vacuum.

Wave speed v=fλ. Period T=1/f. Refraction changes speed and wavelength across media while frequency remains set by the source. Reflection returns a wave, and diffraction spreads it around edges or through gaps.

Superposition adds displacements. Constructive and destructive interference depend on phase differences. Stationary waves have fixed nodes and antinodes. Polarisation restricts transverse oscillation directions; beats arise from nearby frequencies, and Doppler changes result from relative source-observer motion.

Work through an example

A wave has frequency 50 Hz and wavelength 0.4 m. Find speed.

Explanation: v=fλ=50×0.4=20 m s⁻¹.

Watch out: The medium’s particles oscillate; they do not usually travel with the wave over its full path.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

When a wave enters a new medium, which remains unchanged at the boundary?

  1. Wavelength
  2. Direction
  3. Speed
  4. Frequency
Show answer and explanation

Answer D: Frequency

The source fixes the oscillation frequency.

Question 2

A node of a stationary wave has

  1. No surrounding medium
  2. Maximum amplitude
  3. Infinite frequency
  4. Zero displacement amplitude
Show answer and explanation

Answer D: Zero displacement amplitude

Destructive interference fixes a point with zero amplitude.

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18 Waves

Sound, echoes and musical notes

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What you should be able to do

  • Explain sound propagation and reflection
  • Relate pitch, loudness and resonance to wave properties

Understand it

Sound in air is a longitudinal mechanical wave and needs a material medium. An echo is reflected sound heard separately; reverberation is persistence from overlapping reflections. Echo calculations include the outward and return journeys.

Pitch mainly depends on frequency, loudness relates to intensity and perception, and quality depends on waveform and harmonic content. Two instruments can play the same fundamental frequency yet sound different because their harmonics differ.

For a stretched string, fundamental frequency is (1/2L)√(T/μ). An ideal open pipe has fundamental v/(2L), while a pipe closed at one end has v/(4L), neglecting end correction. Resonance occurs when driving matches an allowed vibration mode.

Work through an example

An echo returns after 0.6 s. With sound speed 340 m s⁻¹, how far away is the reflector?

Explanation: Distance=vt/2=340×0.6/2=102 m.

Watch out: Echo time is a round-trip time.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Increasing frequency mainly increases a note’s

  1. Echo distance automatically
  2. Mass
  3. Pitch
  4. Propagation medium
Show answer and explanation

Answer C: Pitch

Higher frequency corresponds to higher perceived pitch.

Question 2

Sound cannot travel through a perfect vacuum because

  1. Its frequency is too high
  2. It has no energy
  3. It needs a material medium
  4. It is always transverse
Show answer and explanation

Answer C: It needs a material medium

Mechanical vibrations require particles to transmit them.

Link to this topic

19 Optics

Light, reflection and mirrors

Read this lesson

What you should be able to do

  • Apply reflection laws
  • Distinguish real and virtual mirror images

Understand it

Light travels approximately in straight lines in a uniform medium, explaining shadows and pinhole images. Luminous objects emit light; non-luminous objects are seen by reflected light. Reflection occurs when light returns from a surface.

The angle of incidence equals the angle of reflection, with both measured from the normal. A plane mirror forms an upright virtual image the same size as the object and equally far behind the mirror as the object is in front.

Concave mirrors can form real or virtual images depending on object position; convex mirrors produce upright diminished virtual images for ordinary real objects. Ray diagrams use principal rays and distinguish actual ray intersections from apparent backward extensions.

Work through an example

An object is 2 m in front of a plane mirror. How far apart are object and image?

Explanation: The image is 2 m behind the mirror, so the separation is 4 m.

Watch out: Angles of incidence and reflection are measured from the normal, not the reflecting surface.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A plane-mirror image is normally

  1. Real and magnified
  2. Virtual and upside down
  3. Real and inverted
  4. Virtual and upright
Show answer and explanation

Answer D: Virtual and upright

The reflected rays appear to come from behind the mirror.

Question 2

A convex mirror is useful for a wide view because it forms

  1. Diminished images
  2. Real images projected onto a screen
  3. Inverted images at all object distances
  4. Magnified real images
Show answer and explanation

Answer A: Diminished images

Diminished virtual images allow a larger field of view.

Link to this topic

20 Optics

Refraction, lenses and optical instruments

Read this lesson

What you should be able to do

  • Use refractive index and total internal reflection
  • Relate lenses to image formation and vision

Understand it

Refraction changes a light ray’s direction when its speed changes across media, except at normal incidence. Refractive index n=c/v. Snell’s law is n₁sin i=n₂sin r. A ray entering a higher-index medium bends towards the normal.

Total internal reflection requires travel from higher to lower refractive index and an incidence angle exceeding the critical angle. Lenses use refraction to form images. A converging lens can form real or virtual images depending on object distance; a diverging lens forms a virtual diminished image for a real object.

Cameras, projectors, microscopes and telescopes use lens or mirror combinations for different purposes. The eye focuses on the retina; myopia is corrected with a diverging lens and hyperopia with a converging lens in the simple model. Use a consistent sign convention for lens calculations.

Work through an example

Find the speed of light in a medium of refractive index 1.5, using c=3×10⁸ m s⁻¹.

Explanation: v=c/n=(3×10⁸)/1.5=2×10⁸ m s⁻¹.

Watch out: Total internal reflection cannot occur from a lower-index medium into a higher-index medium.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A ray entering glass from air obliquely usually bends

  1. Along its original path without refraction
  2. Away from the normal
  3. Along the boundary in every case
  4. Towards the normal
Show answer and explanation

Answer D: Towards the normal

Glass has the higher refractive index.

Question 2

A lens used to correct simple myopia is

  1. A plane glass plate
  2. Diverging
  3. A prism without focusing power
  4. Converging
Show answer and explanation

Answer B: Diverging

It reduces convergence so distant objects focus on the retina.

Link to this topic

21 Optics

Dispersion, colour and electromagnetic waves

Read this lesson

What you should be able to do

  • Explain colour separation and filters
  • Order the electromagnetic spectrum

Understand it

Dispersion separates light into colours because refractive index depends on wavelength. White light contains a range of visible wavelengths; a prism changes their directions by different amounts.

An object’s apparent colour depends on incident light and the wavelengths it reflects or transmits. A coloured filter transmits selected wavelengths and absorbs others. Additive mixing of light and subtractive mixing of pigments are different processes.

From lower to higher frequency, the electromagnetic spectrum runs radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays. All travel at the same speed in vacuum. Uses depend on wavelength and interaction with matter; ionising regions require appropriate protection.

Work through an example

Why can a red object appear dark under pure blue light?

Explanation: It may reflect red wavelengths strongly but absorb most blue light; no red light is present to reflect.

Watch out: A red filter does not manufacture red light from every incoming wavelength.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Which has a higher frequency than visible light?

  1. Radio
  2. Ultraviolet
  3. Microwave
  4. Infrared
Show answer and explanation

Answer B: Ultraviolet

Ultraviolet lies above visible light in frequency.

Question 2

White light splitting into colours in a prism is

  1. Electrolysis
  2. Evaporation
  3. Conduction
  4. Dispersion
Show answer and explanation

Answer D: Dispersion

Different wavelengths refract by different amounts.

Link to this topic

22 Electricity

Electrostatics and capacitance

Read this lesson

What you should be able to do

  • Explain electric forces and fields
  • Calculate charge storage and capacitor energy

Understand it

Like charges repel and unlike charges attract. Charge can be redistributed by friction, contact and induction, while total charge is conserved. Coulomb’s law gives force proportional to q₁q₂/r² for point charges.

An electric field is force per unit positive test charge; field lines point away from positive and towards negative charges. Potential difference is energy transferred per unit charge. Conductors allow mobile charge movement; insulators restrict it.

Capacitance C=Q/V measures stored charge per potential difference. For parallel plates, C=εA/d. Capacitors in parallel add capacitances; in series their reciprocals add. Stored energy is ½CV². A dielectric changes capacitance by changing the material between plates.

Work through an example

A capacitor stores 12 μC at 6 V. Find capacitance.

Explanation: C=Q/V=12/6=2 μF.

Watch out: The electric field direction is defined using a positive test charge.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Doubling separation of ideal parallel capacitor plates makes capacitance

  1. Four times
  2. Half
  3. Double
  4. Unchanged
Show answer and explanation

Answer B: Half

C=εA/d, so capacitance is inversely proportional to separation.

Question 2

Two capacitors of 2 μF and 3 μF in parallel give

  1. 6 μF
  2. 5 μF
  3. 1 μF
  4. 1.2 μF
Show answer and explanation

Answer B: 5 μF

Parallel capacitances add directly.

Link to this topic

23 Electricity

Cells, circuits and resistance

Read this lesson

What you should be able to do

  • Distinguish emf and terminal voltage
  • Solve simple series and parallel circuits

Understand it

Emf is energy supplied per unit charge by a source. A cell with internal resistance r has terminal voltage V=E−Ir while supplying current. Primary cells are not normally designed for recharging; secondary cells are designed for reversible use within safe operating limits.

Current is charge flow per time. Ohm’s law V=IR applies to an ohmic conductor under constant physical conditions. Resistance R=ρL/A depends on material, length and area; resistivity ρ is a material property at a stated temperature.

Series resistances add and share the same current. Parallel branches share voltage and satisfy 1/Rtotal=Σ1/R. An ammeter is connected in series with low resistance; a voltmeter is connected in parallel with high resistance. Bridge and potentiometer methods compare quantities through balanced conditions.

Work through an example

A 6 V source is connected to 3 Ω with negligible internal resistance. Find current.

Explanation: I=V/R=6/3=2 A.

Watch out: Emf is a voltage despite its historical name; it is not a mechanical force.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Two 6 Ω resistors in parallel have equivalent resistance

  1. 3 Ω
  2. 6 Ω
  3. 12 Ω
  4. 36 Ω
Show answer and explanation

Answer A: 3 Ω

For equal parallel resistors, the equivalent is half either resistance.

Question 2

A voltmeter is connected

  1. In series with the component
  2. Across a disconnected isolated wire only
  3. In parallel
  4. In place of the cell
Show answer and explanation

Answer C: In parallel

It compares potential at two points.

Link to this topic

24 Electricity

Electrical power, energy and household protection

Read this lesson

What you should be able to do

  • Calculate electrical power and energy
  • Explain transmission and protective devices

Understand it

For steady direct current, electrical power is P=VI. In an AC circuit, instantaneous power is p=vi; average real power for sinusoidal voltage and current is Vrms Irms cosφ, as explained in the alternating-current lesson. For a resistor, P=I²R=V²/R. Energy transferred is Pt, and 1 kilowatt-hour equals 3.6 million joules. A kilowatt-hour is an energy unit, not a power unit.

For a given transmitted power, increasing voltage reduces current and therefore reduces I²R heating in transmission lines. Transformers support this process in alternating-current systems. Actual networks still have losses and operating limits.

A fuse or circuit breaker interrupts excessive current; earthing gives a protective path in appropriate systems. Household appliances are normally connected in parallel so each receives the supply voltage. Electrical installation and battery maintenance should follow trained supervision and manufacturer instructions.

Work through an example

A 1 kW appliance runs for 2.5 hours. Find energy in kWh.

Explanation: Energy=1×2.5=2.5 kWh.

Watch out: A fuse’s ampere rating concerns current. Real fuses also have voltage and breaking-capacity ratings; do not treat the ampere value as the only safety specification.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

A device draws a steady current of 2 A from a 12 V DC supply. What is its electrical power?

  1. 144 W
  2. 6 W
  3. 14 W
  4. 24 W
Show answer and explanation

Answer D: 24 W

For the stated steady DC supply, P=VI=12×2=24 W.

Question 2

High-voltage transmission reduces losses mainly by reducing

  1. Current for a given power
  2. All resistance to zero
  3. Energy conservation
  4. Frequency to zero
Show answer and explanation

Answer A: Current for a given power

Lower current produces less I²R heating.

Link to this topic

25 Electromagnetism

Magnetic fields and forces

Read this lesson

What you should be able to do

  • Describe fields around magnets and currents
  • Apply force on moving charge and current

Understand it

Magnetic field lines form closed paths and indicate the direction a north pole would tend to move. A current-carrying wire produces a surrounding magnetic field; a solenoid produces a field resembling that of a bar magnet. Soft iron is useful for temporary electromagnets.

Force on a straight wire is F=BIL sinθ. For a moving charge, F=qvB sinθ, perpendicular to velocity and field. Parallel currents attract when they flow in the same direction and repel when opposite.

The motor effect converts electrical input to mechanical motion. A moving-coil meter uses turning force on a coil; a shunt makes it suitable for larger currents and a series multiplier for voltage measurement. Earth’s magnetic field supports compass navigation, with dip and declination describing different angles.

Work through an example

A 0.5 m wire carries 4 A perpendicular to a 0.2 T field. Find force.

Explanation: F=BIL=0.2×4×0.5=0.4 N.

Watch out: Magnetic force on a moving charge is zero when its velocity is parallel to the field.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Two parallel wires carrying current in the same direction

  1. Experience no magnetic force
  2. Attract
  3. Reverse each other’s current automatically
  4. Repel
Show answer and explanation

Answer B: Attract

Their magnetic interaction is attractive.

Question 2

A galvanometer is converted into an ammeter using a low resistance

  1. In series with the coil
  2. In series with the external source only
  3. In parallel
  4. As an insulating replacement for the coil
Show answer and explanation

Answer C: In parallel

A shunt carries most of the current around the sensitive coil.

Link to this topic

26 Electromagnetism

Induction, transformers and inductance

Read this lesson

What you should be able to do

  • Apply Faraday’s and Lenz’s ideas
  • Calculate ideal transformer ratios

Understand it

An emf is induced when magnetic flux linkage changes. Faraday’s law relates its magnitude to the rate of change; Lenz’s law gives a direction opposing the change that produced it. A stationary conductor can experience induction if the field changes.

Generators convert mechanical energy to electrical energy. A transformer uses changing flux between coils; for an ideal transformer, Vs/Vp=Ns/Np and input power equals output power. Ordinary transformers need varying current, rather than steady direct current.

Inductance measures the opposition to a change in current through induced emf. An inductor stores energy ½LI² in its magnetic field. Eddy currents can produce unwanted heating or useful braking and heating; laminated cores reduce many unwanted eddy-current losses.

Work through an example

An ideal transformer has 100 primary turns and 500 secondary turns. With 12 V input, find output voltage.

Explanation: Vs=12×500/100=60 V.

Watch out: A step-up transformer increases voltage while decreasing current for the same ideal power.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Increasing the rate of change of magnetic flux generally increases induced

  1. Emf
  2. Number of turns automatically
  3. Mass of the coil
  4. Electrical resistance of the conductor necessarily
Show answer and explanation

Answer A: Emf

Faraday’s law links emf to flux-change rate.

Question 2

Lenz’s law is consistent with conservation of

  1. Linear momentum alone
  2. Energy
  3. Angular momentum alone
  4. Electric charge alone
Show answer and explanation

Answer B: Energy

The opposing effect prevents energy from appearing without input work.

Link to this topic

27 Electromagnetism

Alternating-current circuits

Read this lesson

What you should be able to do

  • Relate peak and rms quantities
  • Explain reactance, impedance and resonance

Understand it

Alternating current changes direction periodically. For a sinusoidal signal, rms voltage is Vpeak/√2 and rms current is Ipeak/√2. The rms value gives the equivalent heating effect in a resistor.

A resistor has voltage and current in phase. An ideal inductor makes current lag voltage, while an ideal capacitor makes current lead. Inductive reactance is XL=2πfL and capacitive reactance is XC=1/(2πfC).

For a series RLC circuit, impedance magnitude is √[R²+(XL−XC)²]. Resonance occurs when XL=XC, with f₀=1/(2π√LC). Average real power is Vrms Irms cosφ; a phase difference reduces the power factor.

Work through an example

A sinusoidal voltage has peak 100√2 V. Find rms voltage.

Explanation: Vrms=100√2/√2=100 V.

Watch out: Use rms quantities consistently when calculating ordinary AC heating power.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Increasing frequency makes capacitive reactance

  1. Become zero at every nonzero frequency
  2. Decrease
  3. Increase
  4. Remain constant
Show answer and explanation

Answer B: Decrease

XC is inversely proportional to frequency.

Question 2

At series RLC resonance

  1. R must be zero
  2. Frequency must be zero
  3. XL=XC
  4. Current must be zero
Show answer and explanation

Answer C: XL=XC

Inductive and capacitive reactances cancel in the net impedance.

Link to this topic

28 Electricity

Conduction in liquids and gases

Read this lesson

What you should be able to do

  • Identify charge carriers in different media
  • Connect electrolysis with charge transfer

Understand it

In metals, mobile electrons carry current. In electrolytes, positive and negative ions move in opposite directions and transport charge. A liquid containing molecules but few mobile ions can be a poor conductor.

Electrolysis produces chemical changes at electrodes. The cathode is the reduction electrode and the anode the oxidation electrode. The amount of product depends on charge passed and the number of electrons transferred per particle.

A gas normally conducts poorly but can conduct when ionised, supplying ions and free electrons. Electrical discharge can produce light, as in suitable discharge lamps. Conduction mechanisms therefore depend on the state and available charge carriers, not simply whether a material is hot or cold.

Work through an example

How much charge passes through an electrolyte at 0.5 A for 120 s?

Explanation: Q=It=0.5×120=60 C.

Watch out: Electrolyte current is not carried only by electrons moving through the liquid.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

The main charge carriers in an electrolyte are

  1. Free electrons travelling through the liquid as in a metal
  2. Protons confined within nuclei
  3. Ions
  4. Neutral solvent molecules
Show answer and explanation

Answer C: Ions

Both positive and negative ions contribute to current.

Question 2

Ionising a gas generally makes it

  1. Free of charge carriers
  2. Always solid
  3. More able to conduct
  4. A perfect vacuum
Show answer and explanation

Answer C: More able to conduct

Ionisation creates mobile charged particles.

Link to this topic

29 Modern physics

Atoms, photons and modern physics

Read this lesson

What you should be able to do

  • Explain quantised energy and photoelectric emission
  • Distinguish wave and particle descriptions

Understand it

Rutherford’s nuclear model placed most atomic mass and positive charge in a small nucleus. Bohr’s model introduced quantised energy levels for simple atoms. Modern quantum descriptions replace fixed classical orbits with more general probability-based states.

A photon has energy E=hf. In the photoelectric effect, light above a threshold frequency can eject electrons; maximum kinetic energy is hf−work function. Increasing intensity at fixed suitable frequency increases electron emission rather than the maximum kinetic energy.

Thermionic emission releases electrons through heating. X-rays can be produced when fast electrons strike a target. Electron diffraction supports wave behaviour of matter; de Broglie wavelength is h/p. Quantum uncertainty concerns limits on simultaneous precision of certain paired quantities, not merely poor instruments.

Work through an example

A photon has energy 5 eV and a metal’s work function is 2 eV. Find maximum photoelectron kinetic energy.

Explanation: Kmax=5−2=3 eV.

Watch out: Below threshold frequency, greater intensity alone does not supply more energy per photon.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Photon energy increases with

  1. Frequency
  2. Mass of a mirror only
  3. Wavelength in direct proportion
  4. Surface area only
Show answer and explanation

Answer A: Frequency

E=hf.

Question 2

Electron diffraction supports the idea that electrons

  1. Are sound waves
  2. Are always stationary
  3. Have wave behaviour
  4. Have no momentum
Show answer and explanation

Answer C: Have wave behaviour

Diffraction is a wave-like phenomenon.

Link to this topic

30 Modern physics

Radioactivity, nuclear energy and half-life

Read this lesson

What you should be able to do

  • Balance nuclear changes
  • Calculate remaining fractions and mass-energy changes

Understand it

Alpha radiation is a helium nucleus, beta-minus radiation is an emitted electron from nuclear conversion, and gamma radiation consists of high-energy photons. They differ in ionising ability, penetration and response to fields.

The number of undecayed nuclei follows N=N₀(1/2)^(t/T½), with half-life related to decay constant by T½=ln2/λ. Individual decay is unpredictable, while a large population has a predictable statistical pattern.

Fission splits heavy nuclei and fusion joins light nuclei. The energy difference is related to mass defect by ΔE=Δmc². Binding energy describes the energy required to separate a nucleus into its nucleons and helps explain nuclear stability.

Work through an example

What fraction remains after three half-lives?

Explanation: (1/2)³=1/8, or 12.5% of the initial undecayed amount.

Watch out: Radiation shielding depends on radiation type and exposure conditions; penetration and ionisation are different properties.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Which radiation is not deflected by an electric field?

  1. Gamma
  2. Beta-minus
  3. Alpha
  4. A proton beam
Show answer and explanation

Answer A: Gamma

Gamma photons have no electric charge.

Question 2

Splitting a heavy nucleus is called

  1. Condensation
  2. Refraction
  3. Fusion
  4. Fission
Show answer and explanation

Answer D: Fission

Fission breaks a nucleus into smaller nuclear products.

Link to this topic

31 Electronics

Semiconductors, diodes and transistors

Read this lesson

What you should be able to do

  • Compare conductors, insulators and semiconductors
  • Explain doping, rectification and amplification

Understand it

Electrical behaviour depends partly on energy bands and available charge carriers. Semiconductors have a smaller relevant band gap than typical insulators, and their conductivity can be changed by temperature, light and added impurities.

An intrinsic semiconductor is relatively pure. Donor doping creates n-type material with electrons as majority carriers; acceptor doping creates p-type material with holes as majority carriers. The material remains electrically neutral overall despite these names.

A p-n junction diode conducts much more readily under forward than reverse bias within its normal range. Rectification converts alternating input into a unidirectional output. A transistor can control a larger current using a smaller input and supports amplification and switching.

Work through an example

Why is a diode useful in a simple rectifier?

Explanation: Its directional conduction allows current during one polarity more readily than the other, producing a unidirectional output.

Watch out: n-type does not mean the entire piece of material has a net negative charge.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Majority carriers in p-type material are

  1. Only photons
  2. Protons moving through the lattice
  3. Holes
  4. Neutrons
Show answer and explanation

Answer C: Holes

Acceptor doping creates mobile hole behaviour.

Question 2

A common use of a transistor is

  1. Amplification
  2. Creating mass
  3. Removing gravity
  4. Measuring rainfall directly
Show answer and explanation

Answer A: Amplification

A small input can control a larger electrical output.

Link to this topic

32 Modern applications

Fibre optics and lasers

Read this lesson

What you should be able to do

  • Explain optical guiding and laser properties
  • Connect physical principles to applications

Understand it

An optical fibre has a core surrounded by cladding with lower refractive index. Suitable rays can be guided by total internal reflection at the boundary. Light signals can carry information over long distances with appropriate sources and detectors.

A laser uses stimulated emission and an optical system to produce a strongly directed, coherent light beam with a narrow range of wavelengths. Coherence concerns a stable phase relationship, while monochromaticity concerns wavelength range.

Fibre optics support communication and imaging systems; lasers are used in measurement, manufacturing, medicine and data technologies. Real fibres have losses and dispersion, and real laser beams are not perfectly monochromatic or perfectly parallel.

Work through an example

Why should the fibre core have a higher refractive index than the cladding?

Explanation: That arrangement allows total internal reflection for suitable angles at the core-cladding boundary.

Watch out: Total internal reflection also requires the incidence angle to exceed the critical angle.

2 practice questions with answers

Try each question before opening its answer. These are original CampusNinja practice questions.

Question 1

Optical fibres mainly guide light using

  1. Total internal reflection
  2. Electrolysis
  3. Nuclear fusion
  4. Sound resonance
Show answer and explanation

Answer A: Total internal reflection

Light can remain confined by repeated internal reflection.

Question 2

Laser light is characteristically

  1. Necessarily white
  2. Always sound
  3. Always harmless to eyes
  4. Coherent and strongly directed
Show answer and explanation

Answer D: Coherent and strongly directed

Stimulated emission supports a consistent phase relationship and a directed beam.

Link to this topic

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Scope checked against JAMB’s IBASS source on 2026-10-16. Current IBASS file; not independently labelled 2027. Notes, examples and practice questions are original CampusNinja learning material, not authenticated JAMB past questions.

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