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Edexcel IGCSE Physics

Topic questions Waves Total internal reflection & optical fibres

Total internal reflection & optical fibres

12 questions · 121 marks · about 2 hours

Total internal reflection and optical fibres questions

TopicTotal internal reflection & optical fibres

Edexcel 4PH1 Total internal reflection and optical fibres 12 questions

Physics Paper 1 June 2025 (R), Question 7 11 marks

This question is about light.

(a)

Light is an example of a transverse wave.

Describe a transverse wave.

You may draw a diagram to help your answer.

[2]
(b)

Diagram 1 shows a ray of light in a section of optical fibre.

Figure for question 7

Diagram 1

(b)(i)

The ray of light is incident at the boundary between the optical fibre and air.

The ray of light reflects at the boundary.

Complete diagram 1 by drawing the reflected ray of light.

[2]
Reveal mark scheme Mark scheme for question 7(b)(i)
(b)(ii)

Explain why no light leaves the optical fibre when the light reflects at the boundary between the optical fibre and air.

[3]
Reveal mark scheme Mark scheme for question 7(b)(ii)
(c)

Diagram 2 shows a different ray of light, incident on the boundary between water

Figure for question 7

Using diagram 2, show that the refractive index of water is approximately 1.3

[4]
Reveal mark scheme Mark scheme for question 7(c)

Physics Paper 1 November 2024, Question 6 13 marks

A student does an investigation to determine the refractive index of a rectangular block of transparent material.

The student uses this equipment in their investigation.

• ray box

• rectangular transparent block

• protractor

• pencil

• paper

• ruler

This is the formula linking refractive index, angle of incidence and angle of refraction.

Question 6, shown as an image
(a)

Describe a method to determine the refractive index of the material.

You may draw a diagram to help your answer.

[5]
(b)

The refractive index of the material is 1.2

(b)(i)

State the formula linking the refractive index and the critical angle of a material.

[1]
Reveal mark scheme Mark scheme for question 6(b)(i)
(b)(ii)

Calculate the critical angle of this material.

critical angle =........ degrees

[2]
Reveal mark scheme Mark scheme for question 6(b)(ii)
(b)(iii)

Describe what is meant by the term total internal reflection.

[2]
Reveal mark scheme Mark scheme for question 6(b)(iii)
(c)

The diagram shows a ray of light entering a prism made of the same material as the rectangular block used in the student’s investigation.

Figure for question 6
(c)(i)

Use a protractor to determine the angle of incidence at the point where the ray of light is incident on side AB of the prism.

angle of incidence =........ degrees

[1]
(c)(ii)

Complete the path of the ray of light.

[2]
Reveal mark scheme Mark scheme for question 6(c)(ii)

Physics Paper 1 June 2024, Question 8 6 marks

The diagram shows two rays of light, A and B, incident on the boundary between air and water.

Figure for question 8
Question 8, shown as an image

The refractive index of water is 1.33

Explain the paths of the two rays of light after they strike the boundary between air and water.

Include calculations in your answer and draw on the diagram to support your answer.

[6]
Reveal mark scheme Mark scheme for question 8

Physics Paper 1 January 2023, Question 6 6 marks

This question is about optical fibres.

(a)

Optical fibres use light waves for communication.

Which of these is a correct statement about waves?

Question 6, shown as an image
[1]
Reveal mark scheme Mark scheme for question 6(a)
(b)

A ray of light passes from air into a glass optical fibre.

Diagram 1 shows the path of the ray of light after it has passed through the boundary between air and the optical fibre.

(b)(i)

Draw the path of the ray of light in air before it passed through the boundary.

Figure for question 6
[1]
Reveal mark scheme Mark scheme for question 6(b)(i)
(b)(ii)

Diagram 1

State the name of the wave behaviour responsible for the path of the ray of light as it passes from air into the optical fibre.

[1]
Reveal mark scheme Mark scheme for question 6(b)(ii)
(c)

Diagram 2 shows the path of the ray of light as it travels through the optical fibre.

Figure for question 6

Explain the path of the ray of light as it travels through the optical fibre.

[3]
Reveal mark scheme Mark scheme for question 6(c)

Physics Paper 1 January 2023 (R), Question 7 9 marks

The diagram shows the path of a ray of light.

Figure for question 7
(a)(i)

Measure the angle of incidence for the ray at point K.

Which of these is the angle of incidence?

Question 7, shown as an image
[1]
Reveal mark scheme Mark scheme for question 7(a)(i)
(a)(ii)

State the formula linking refractive index, angle of incidence and angle of refraction.

[1]
(a)(iii)

The block has a refractive index of 1.52

Use the formula to show that the angle of refraction is about 30° for the ray at point K.

[3]
Reveal mark scheme Mark scheme for question 7(a)(iii)
(b)(i)

The refractive index of the block is 1.52

Calculate the critical angle of the block.

[3]
Reveal mark scheme Mark scheme for question 7(b)(i)
(b)(ii)

State what happens to the ray at point L.

[1]
Reveal mark scheme Mark scheme for question 7(b)(ii)

Physics Paper 2 June 2022 (R), Question 6 12 marks

Also involves Errors and uncertainties

The refractive index, n, of a material can be calculated using this formula.

Question 6, shown as an image
(a)

A student uses this method to determine the refractive index of a material.

• draw around a semi-circular block of material

• shine a light ray towards the centre of the straight edge of the semi‑circular block

• use a pencil and a ruler to mark the positions of the incident ray and the refracted ray

• remove the block

• draw a normal where the ray was incident on the block

• measure the angle of incidence and angle of refraction

• calculate the refractive index using the formula

Repeat the method for different angles of incidence.

(a)(i)

Name the independent variable in this investigation.

[1]
Reveal mark scheme Mark scheme for question 6(a)(i)
(a)(ii)

The table shows the student’s results for an angle of incidence of 40°.

Angle of refraction 1 (°)Angle of refraction 2 (°)Angle of refraction 3 (°)
222367

Calculate the mean value for the angle of refraction.

mean angle =........ degrees

[2]
Reveal mark scheme Mark scheme for question 6(a)(ii)
(a)(iii)

Describe how the student could improve their method to get a more accurate value for the refractive index.

[2]
Reveal mark scheme Mark scheme for question 6(a)(iii)
(b)

Diagram 1 shows a ray of light refracted by a transparent block of material.

Figure for question 6
(b)(i)

Calculate the refractive index of this material.

[2]
Reveal mark scheme Mark scheme for question 6(b)(i)
(b)(ii)

State the formula linking critical angle and refractive index.

[1]
(b)(iii)

The refractive index of a different material is 1.7

Calculate the critical angle of this material.

critical angle =........ degrees

[2]
Reveal mark scheme Mark scheme for question 6(b)(iii)
(c)

Diagram 2 shows a ray of light travelling through an optical fibre.

Figure for question 6

The optical fibre is made of a material with a refractive index of 1.7

Explain the path of the ray in the optical fibre.

[2]
Reveal mark scheme Mark scheme for question 6(c)

Physics Paper 1 January 2022 (R), Question 7 8 marks

(a)

Describe an experiment to determine the refractive index of a glass block.

In your answer you should include

• a labelled diagram

• the apparatus needed

• the method used

[6]
Reveal mark scheme Mark scheme for question 7(a)
(b)

Give two uses of total internal reflection.

[2]
Reveal mark scheme Mark scheme for question 7(b)

Physics Paper 1 November 2020, Question 8 11 marks

Also involves Refractive index and Snell's law

This question is about atmospheric optical illusions.

(a)

A mirage is an optical illusion formed due to total internal reflection of light from the sky at the boundary between cold air and hot air.

Diagram 1 shows how a mirage is formed.

Figure for question 8
(a)(i)

State the formula linking critical angle and refractive index.

[1]
Reveal mark scheme Mark scheme for question 8(a)(i)
(a)(ii)

The critical angle of the cold air at the boundary is 88.500°

Calculate the refractive index of the cold air.

Give your answer to 5 significant figures.

[3]
Reveal mark scheme Mark scheme for question 8(a)(ii)
(b)(i)

Diagram 2 shows a ray of light from the Sun.

The refractive index of the atmosphere is greater than the refractive index of space.

Complete the diagram by drawing the path of the ray of light through the atmosphere.

Figure for question 8
[2]
Reveal mark scheme Mark scheme for question 8(b)(i)
(b)(ii)

Diagram 3 shows a ray of light from the Sun when the Sun is directly overhead.

Figure for question 8

Explain why the ray of light does not change direction when it enters the atmosphere.

[2]
Reveal mark scheme Mark scheme for question 8(b)(ii)
(b)(iii)

Explain why the wavelength of the light reduces when it enters the atmosphere.

[2]
Reveal mark scheme Mark scheme for question 8(b)(iii)
(b)(iv)

Suggest why the Sun appears not to be circular when it is close to the horizon at sunset.

[1]
Reveal mark scheme Mark scheme for question 8(b)(iv)

Physics Paper 1 November 2020 (R), Question 12 7 marks

This question is about refraction.

(a)

Diagram 1 shows a ray of light incident on the boundary between a liquid called acetone and air.

Figure for question 12
(a)(i)

Calculate the critical angle for the boundary between acetone, and air.

[1]
Reveal mark scheme Mark scheme for question 12(a)(i)
(a)(ii)

State the formula linking critical angle and refractive index.

[1]
(a)(iii)

Calculate the refractive index of acetone.

[2]
Reveal mark scheme Mark scheme for question 12(a)(iii)
(b)

Diagram 2 shows a ray of light incident on the boundary between water and air.

Figure for question 12

Explain how the refractive index of water compares to the refractive index of acetone.

[3]
Reveal mark scheme Mark scheme for question 12(b)

Physics Paper 1 January 2020, Question 10 11 marks

This question is about light.

(a)

Diagram 1 shows a light ray entering a glass prism.

Figure for question 10
(a)(i)

Describe what happens to the light ray when it enters the prism at point A.

[2]
Reveal mark scheme Mark scheme for question 10(a)(i)
(a)(ii)

State the name of line XY.

[1]
(a)(iii)

State the formula linking critical angle and refractive index.

[1]
Reveal mark scheme Mark scheme for question 10(a)(iii)
(a)(iv)

The refractive index for the glass in this prism is 1.6

Calculate the critical angle for the glass in this prism.

[3]
Reveal mark scheme Mark scheme for question 10(a)(iv)
(a)(v)

Complete Diagram 1 by continuing the path of the light ray from point B.

[2]
Reveal mark scheme Mark scheme for question 10(a)(v)
(b)

Diagram 2 shows a similar prism that is made from a material with a different refractive index.

The critical angle for the material of this prism is 55°

Complete Diagram 2 by continuing the path of the light ray.

Figure for question 10
[2]
Reveal mark scheme Mark scheme for question 10(b)

Physics Paper 1 June 2019, Question 7 14 marks

Question 7, shown as an image
(a)
Question 7, shown as an image
[1]
Reveal mark scheme Mark scheme for question 7(a)
Question 7, shown as an image
Figure for question 7
Question 7, shown as an image
(b)(i)
Question 7, shown as an image
[2]
Reveal mark scheme Mark scheme for question 7(b)(i)
(b)(ii)
Question 7, shown as an image
[1]
Reveal mark scheme Mark scheme for question 7(b)(ii)
(b)(iii)
Question 7, shown as an image
[2]
Reveal mark scheme Mark scheme for question 7(b)(iii)
(c)
Question 7, shown as an image
(c)(i)
Question 7, shown as an image
[2]
Reveal mark scheme Mark scheme for question 7(c)(i)
(c)(ii)
Question 7, shown as an image
[1]
Reveal mark scheme Mark scheme for question 7(c)(ii)
(c)(iii)
Question 7, shown as an image
Question 7, shown as an image
[3]
Reveal mark scheme Mark scheme for question 7(c)(iii)
(c)(iv)
Question 7, shown as an image
Question 7, shown as an image
Figure for question 7
[2]
Reveal mark scheme Mark scheme for question 7(c)(iv)

Physics Paper 1 June 2019 (R), Question 9 13 marks

(a)

A light ray travels from air into water.

Diagram 1 shows the direction of the light ray and the wavefronts in air.

Figure for question 9

Diagram 1

The refractive index of water is greater than the refractive index of air.

(a)(i)

Complete diagram 1 by showing

● the wavefronts in the water

● the path of the light ray in the water

[3]
Reveal mark scheme Mark scheme for question 9(a)(i)
(a)(ii)

Explain what happens to the wavelength of light when it passes from air into water.

[2]
Reveal mark scheme Mark scheme for question 9(a)(ii)
(b)

Diagram 2 shows what can happen when a light ray travelling in glass meets the boundary with air.

The wavefronts are not shown in this diagram.

Question 9, shown as an image
Figure for question 9

Diagram 2

(b)(i)

Add the normal to diagram 2.

[1]
Reveal mark scheme Mark scheme for question 9(b)(i)
(b)(ii)

Measure the angle of incidence in diagram 2.

angle of incidence =........ degrees

[1]
Reveal mark scheme Mark scheme for question 9(b)(ii)
(b)(iii)

The glass has a refractive index of 1.6

Calculate the critical angle of the glass-air boundary.

critical angle =........ degrees

[3]
Reveal mark scheme Mark scheme for question 9(b)(iii)
(b)(iv)

Explain the path of the light ray shown in diagram 2.

[3]
Reveal mark scheme Mark scheme for question 9(b)(iv)

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