Edexcel IGCSE Physics D Light and Sound Questions

Practise interpreting light and sound diagrams, measuring angles, applying refraction equations, and explaining reflection or total internal reflection.

Exam points

draw reflected rays with angle of reflection equal to angle of incidence
measure incidence, refraction or critical angles from ray diagrams and use sin c = 1/n
interpret sound-wave statements, including longitudinal waves and reflection or refraction

Covered syllabus points

3.14 Light waves 3.15 Law of reflection 3.16 Ray diagrams 3.17 Refraction practical 3.18 Refractive index equation 3.19 Glass refractive index practical 3.20 Total internal reflection 3.21 Critical angle 3.22 Critical angle equation 3.23 Sound waves 3.24P Human hearing range 3.25P Speed of sound practical 3.26P Oscilloscope and microphone 3.27P Sound frequency practical 3.28P Pitch and frequency 3.29P Loudness and amplitude

[Maximum number: 11]

This question is about light.

(a)

Diagram 1 shows a light ray entering a glass prism.

Diagram 1

[ 9 ]

(i)

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

[ 2 ]

(ii)

State the name of line XY .

[ 1 ]

(iii)

State the formula linking critical angle and refractive index.

[ 1 ]

$\sin (\mathrm{c})=1 / \mathrm{n} ;$

Notes: allow in words and
rearrangements

(iv)

The refractive index for the glass in this prism is 1.6.

Calculate the critical angle for the glass in this prism.

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

[ 3 ]

(v)

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

[ 2 ]

(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 degrees.

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

Diagram 2

[ 2 ]

[Maximum number: 12]

A student does an investigation to determine the refractive index of a block made from flint glass.

(a)

She directs a ray of red light at the block, as shown in diagram 1.

Diagram 1

[ 9 ]

(i)

Some of the light is reflected from the surface of the block at point A . On diagram 1, draw this reflected ray of light.

[ 1 ]

(ii)

Use a protractor to determine the angle of incidence and the angle of refraction of the red light at point A on diagram 1.

angle of incidence = ...... degrees

angle of refraction = ...... degrees

[ 2 ]

(iii)

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

[ 1 ]

(iv)

Calculate the refractive index of the glass for red light.

refractive index = ............

[ 2 ]

(v)

Describe how the student could improve her investigation to obtain a more reliable value of the refractive index.

[ 3 ]

(b)

The student replaces the red light with a blue light.

Diagram 2 shows a ray of blue light directed at point A, at the same angle of incidence as the previous ray of red light.

The dashed lines on diagram 2 show the previous path of the ray of red light.

Diagram 2

The refractive index of flint glass for blue light is higher than the refractive index of flint glass for red light.

Complete diagram 2 by drawing the path of blue light from point A until it passes into air.

[ 3 ]

[Maximum number: 13]

This question is about refraction.

(a)

The diagram shows a ray of light from a torch incident on the surface of a pool of water.

Figure for Question (a) — Edexcel IGCSE Physics

The angle of refraction of the ray of light is $33^{\circ}$

[ 5 ]

(i)

Draw the path of the ray of light in the water.

[ 2 ]

(ii)

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

[ 1 ]

(iii)

Show that the refractive index of water is about 1.3

[ 2 ]

Marking points:
- substitution
- evaluation to at least 3 significant figures

Example:
$n=\frac{\sin45^\circ}{\sin33^\circ}$ n=1.30

Do not accept:
- 45/33
- 1.36

Marking guidance:
- reverse argument scores 1 mark only, e.g. calculating i or r using n
- allow $1.298\ldots$
- condone 1.29

(b)

The torch is moved below the surface of the water. Light from the torch is incident on the water surface at an angle greater than the critical angle.

[ 8 ]

(i)

Explain the meaning of the term critical angle.

You may draw a diagram to help your answer.

[ 2 ]

(ii)

State the formula linking critical angle and refractive index.

[ 1 ]

(iii)

Calculate the critical angle of water.

Assume the refractive index of water is 1.3

[ 3 ]

(iv)

A ray of light leaves the torch as shown in the diagram.

Complete the path of the ray of light.

Figure for Question (iv) — Edexcel IGCSE Physics

[ 2 ]

[Maximum number: 2]

This question is about light.

Diagram 1 shows a light ray entering a glass prism.

Diagram 1

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

[Maximum number: 1]

A student does an investigation to determine the refractive index of a block made from flint glass.

She directs a ray of red light at the block, as shown in diagram 1.

Diagram 1

Some of the light is reflected from the surface of the block at point A . On diagram 1, draw this reflected ray of light.

[Maximum number: 2]

This question is about refraction.

The diagram shows a ray of light from a torch incident on the surface of a pool of water.

Figure for Question 6 — Edexcel IGCSE Physics

The angle of refraction of the ray of light is $33^{\circ}$

Draw the path of the ray of light in the water.

[Maximum number: 2]

A student does an investigation to determine the refractive index of a block made from flint glass.

She directs a ray of red light at the block, as shown in diagram 1.

Diagram 1

Use a protractor to determine the angle of incidence and the angle of refraction of the red light at point A on diagram 1.

angle of incidence = ...... degrees

angle of refraction = ...... degrees

[Maximum number: 3]

A student does an investigation to determine the refractive index of a block made from flint glass.

She directs a ray of red light at the block, as shown in diagram 1.

Diagram 1

Describe how the student could improve her investigation to obtain a more reliable value of the refractive index.

[Maximum number: 2]

This question is about refraction.

The torch is moved below the surface of the water. Light from the torch is incident on the water surface at an angle greater than the critical angle.

A ray of light leaves the torch as shown in the diagram.

Complete the path of the ray of light.

Figure for Question 9 — Edexcel IGCSE Physics

[Maximum number: 2]

This question is about refraction.

The torch is moved below the surface of the water. Light from the torch is incident on the water surface at an angle greater than the critical angle.

Explain the meaning of the term critical angle.

You may draw a diagram to help your answer.

[Maximum number: 3]

This question is about sound waves.

(a)

Sound is an example of a type of wave.

State the name of this type of wave.

[ 1 ]

(b)

The speed of sound in liquids is greater than the speed of sound in gases.

[ 2 ]

(i)

Suggest why the speed of sound in liquids is greater than the speed of sound in gases.

[ 2 ]

[Maximum number: 2]

Magnetic Resonance Imaging (MRI) machines can take scans of the inside of a patient.

During the scan, music can be played through a loudspeaker to the patient.

The oscilloscope trace in the diagram represents a sound played to the patient.

Figure for Question 12 — Edexcel IGCSE Physics

Deduce whether humans can hear the sound wave.

[Maximum number: 5]

This question is about sound waves.

Describe an experiment to measure the speed of sound in air.

You may draw a diagram to help your answer.

[Maximum number: 2]

This question is about sound.

A sound wave has a frequency of 500 Hz .

The diagram shows the screen of an oscilloscope.

The timebase of the oscilloscope is 0.50 ms per square.

Figure for Question 14 — Edexcel IGCSE Physics

Draw the trace on the oscilloscope screen when the sound wave is detected.

[Maximum number: 3]

Magnetic Resonance Imaging (MRI) machines can take scans of the inside of a patient.

During the scan, music can be played through a loudspeaker to the patient.

The oscilloscope trace in the diagram represents a sound played to the patient.

Figure for Question 15 — Edexcel IGCSE Physics

Determine the period of the sound wave.

period = ............ s

Marking points:
- period given as 4 squares
- correct use of x scale
- subsequent correct evaluation of period

Example:
$\text{period}=4\ \text{squares}$ $\text{period}=4\times\frac{0.50}{1000}$ $\text{period}=2.0\times10^{-3}\ \mathrm{s}$

Accept:
- ECF candidate's reading of period in squares
- $2.0\ \mathrm{ms}$

Marking guidance:
- Deduct 1 mark for a power-of-ten error.

[Maximum number: 1]

This question is about sound.

State which wave property determines the pitch of a sound.

[Maximum number: 2]

This question is about sound waves.

An oscilloscope can be used to display a sound wave.

The diagram shows the trace on an oscilloscope screen when a sound wave is detected.

Figure for Question 17 — Edexcel IGCSE Physics

On the screen, draw the trace for a quieter sound wave with a lower frequency.

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Covered syllabus points

Question 1

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Question 2

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Question 3

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Question 12

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