Free Reflection & refraction questions for IGCSE Physics (0625), part of Waves. Each question has the answer and the marking points an examiner would look for.
Generate a full Reflection & Refraction worksheet →All Waves questionsA ray of light in a glass block of refractive index 1.6 strikes the glass–air surface at an angle of incidence of 32°.
What happens to the ray?
Answer: D
Light travels through the glass core of an optical fibre at 2.00 × 108 m/s. The speed of light in air is 3.0 × 108 m/s.
Calculate the refractive index of the glass.
Calculate the critical angle for the glass–air boundary.
Light inside the fibre strikes the side of the core at an angle of incidence of 75°. Explain what happens to this light and why.
The fibre is 2.0 km long. Light that travels straight along the axis takes less time than light that reflects many times from side to side. Light reflecting at 75° travels a path 1/sin 75° times as long as the fibre. Calculate the difference in arrival times.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 1.5 n = speed in air ÷ speed in glass C1 1.5 A1 | 2 |
| (b) | 41.8° sin c = 1 ÷ n C1 41.8 A1 | 2 |
| (c) | Totally internally reflected because 75° is greater than the critical angle (41.8°) and the light is travelling from glass to air total internal reflection B1 angle of incidence > critical angle (41.8°), glass → air B1 | 2 |
| (d) | 3.5 × 10−7 s time along axis = 2000 ÷ 2.00 × 108 = 1.00 × 10−5 s C1 zig-zag path time = 1.04 × 10−5 s C1 3.5 × 10−7 A1 | 3 |
A ray of light passes from air into a glass block of refractive index 1.52.
State what is meant by the normal.
The angle of incidence is 50°. Calculate the angle of refraction.
Explain why the ray bends towards the normal as it enters the glass.
Calculate the critical angle for the glass.
State the two conditions needed for total internal reflection.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | line at right angles to the surface where the ray strikes a line perpendicular to the surface at the point where the ray meets it B1 | 1 |
| (b) | 30.3° sin r = sin 50° / 1.52 C1 30.3° A1 | 2 |
| (c) | light slows down in glass light travels more slowly in glass than in air B1 | 1 |
| (d) | 41.1° sin c = 1/1.52 C1 41.1° A1 | 2 |
| (e) | light travels from denser to less dense medium; angle of incidence greater than critical angle light travels from a medium of higher refractive index towards one of lower refractive index B1 angle of incidence is greater than the critical angle B1 | 2 |
A plane mirror forms an image of an object.
State the law of reflection.
State three properties of the image formed by a plane mirror.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | angle of incidence = angle of reflection angle of incidence = angle of reflection B1 | 1 |
| (b) | virtual, upright, same size, same distance behind Any 3 of: virtual; upright; same size; same distance behind the mirror as the object; laterally inverted B3 | 3 |
Light from a white light source passes through a glass prism.
Name the effect seen.
State the order of the colours of the spectrum, starting with the one deviated least.
Explain why violet light is deviated more than red light.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | dispersion dispersion B1 | 1 |
| (b) | red orange yellow green blue indigo violet red, orange, yellow, green, blue, indigo, violet B1 | 1 |
| (c) | slows more / higher refractive index violet light slows down more in glass (the glass has a larger refractive index for violet) B1 | 1 |
This question is about reflection of light.
State the law of reflection.
A ray strikes a plane mirror at an angle of incidence of 30°. Calculate the angle between the incident ray and the mirror surface, and the angle between the incident and reflected rays.
Describe the image formed by a plane mirror.
Explain why the image in a plane mirror is described as virtual.
White light passes through a glass prism and forms a spectrum. Explain why the light is dispersed.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | angle of incidence = angle of reflection angle of incidence equals angle of reflection B1 | 1 |
| (b) | 60°; 60° 60° B1 60° B1 | 2 |
| (c) | virtual; upright; same size; same distance behind mirror; laterally inverted Any 3 of: virtual; upright; same size as the object; same distance behind the mirror as the object is in front; laterally inverted B3 | 3 |
| (d) | rays only appear to come from it; cannot be formed on a screen the rays only appear to come from the image / it cannot be formed on a screen B1 | 1 |
| (e) | different colours (frequencies) travel at different speeds in glass; refracted by different amounts; violet most different colours have different frequencies / wavelengths B1 they travel at different speeds in glass so are refracted by different amounts B1 violet is refracted most and red least B1 | 3 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in