About Light in O Level Physics
Light is one of the 14 main topics in our O Level Physics (Cambridge (CAIE) 5054) question bank, and about 6% of its real questions come from it. Tayyari Karo has 40 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2; 34 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 19 medium, 15 hard, 6 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 6 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
May/June 2026 · Paper 1 · Light
Three students suggest an advantage of using optical fibre cables in telecommunications rather than using copper cables.
1 Optical fibre cables are more secure.
2 Optical fibre cables transmit over greater distances without boosting the signal.
3 Optical fibre cables transmit data at a greater rate.
Which suggestions are correct?
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
Show answer and explanation
Answer: A. 1, 2 and 3
Optical fibres are harder to tap, lose less signal over distance and carry data at higher rates than copper cables, so all three are correct.
May/June 2025 · Paper 1 · Light
Parallel rays of light from a ray-box pass in turn through three lenses at positions 1, 2 and 3.
After the lens at position 1 the rays converge to a point and then spread out again.
After the lens at position 2 the rays travel parallel to one another.
After the lens at position 3 the rays spread apart.
Which type of lens is used at each position?
- 1 converging, 2 converging, 3 converging
- 1 converging, 2 converging, 3 diverging
- 1 diverging, 2 converging, 3 diverging
- 1 diverging, 2 diverging, 3 converging
Show answer and explanation
Answer: B. 1 converging, 2 converging, 3 diverging
Lens 1 brings a parallel beam to a focus and lens 2 turns a diverging beam back into a parallel beam, so both converge light, while lens 3 spreads a parallel beam out and so is diverging.
Oct/Nov 2025 · Paper 1 · Light
The following lists show colours of the spectrum.
Which list shows these colours in order of increasing frequency?
- blue → violet → red → orange → yellow → green
- green → blue → violet → red → orange → yellow
- red → orange → violet → yellow → green → blue
- red → orange → yellow → green → blue → violet
Show answer and explanation
Answer: D. red → orange → yellow → green → blue → violet
Frequency increases from red through the spectrum to violet: red, orange, yellow, green, blue, violet.
May/June 2023 · Paper 1 · Light
A ray of light strikes a plane mirror so that the ray makes an angle of 45° with the mirror surface. The mirror can be rotated about an axis through the point where the ray strikes it.
The mirror is rotated until the light is reflected back along its original path. Through what angle is the mirror rotated?
- 22.5°
- 45°
- 67.5°
- 90°
Show answer and explanation
Answer: B. 45°
Light returns along its own path only when it hits the mirror normally, so the mirror must be turned from 45° to 90° to the ray, a rotation of 45°.
Oct/Nov 2023 · Paper 1 · Light
Which statement is correct?
- Total internal reflection only occurs when light travels from air into glass.
- The larger the refractive index of glass, the larger is the critical angle.
- When total internal reflection occurs, the angle of incidence is equal to the angle of reflection.
- When total internal reflection occurs, the angle of incidence is less than the critical angle.
Show answer and explanation
Answer: C. When total internal reflection occurs, the angle of incidence is equal to the angle of reflection.
Total internal reflection is a case of reflection, so the angle of incidence still equals the angle of reflection; it requires light travelling from a denser to a less dense medium at an angle greater than the critical angle, and a larger refractive index gives a smaller critical angle (sinC = 1/n).
May/June 2021 · Paper 1 · Light
Light travels from a liquid into the air. The refracted ray in the air makes an angle of 32° with the normal.
The refractive index for light moving from air into the liquid is 1.4.
What is the angle of incidence in the liquid?
- 22°
- 37°
- 41°
- 45°
Show answer and explanation
Answer: A. 22°
Using n = sin(angle in air) ÷ sin(angle in liquid), sin(angle in liquid) = sin 32° ÷ 1.4 = 0.379, giving about 22°.
