An echo is the reflection of a sound wave.

Define rarefaction (in a longitudinal wave).

A rarefaction is a region of a longitudinal wave where the lines are drawn further apart, representing lower density/pressure as the wave passes.

How do particles vibrate in a transverse wave such as light, relative to the direction of energy transfer?

In a transverse wave, particles vibrate at right angles ( perpendicular ) to the direction of energy transfer.

Name two behaviours that both light and sound waves can undergo.

Both light and sound waves can undergo reflection and refraction .

In a longitudinal wave diagram, lines drawn closer together represent ______ , while lines drawn further apart represent rarefactions.

In a longitudinal wave diagram, lines drawn closer together represent compressions , while lines drawn further apart represent rarefactions.

True or False? Light is a longitudinal wave.

False. Light is a transverse wave (part of the electromagnetic spectrum); sound is the longitudinal wave.

Define reflection (of a wave).

Reflection occurs when a wave hits a boundary between two media and does not pass through, but instead stays in the original medium.

Define refraction (of a wave).

Refraction occurs when a wave passes a boundary between two different transparent media and undergoes a change in direction.

State the law of reflection .

The angle of incidence ( i ) equals the angle of reflection ( r ), both measured from the normal .

When light travels from a less dense medium into a more dense medium (e.g. air to glass), which way does it bend relative to the normal?

The light bends towards the normal.

Does the frequency of light change when it refracts? Explain your answer.

No. Frequency does not change during refraction — only speed and wavelength change. This is why light does not change colour when refracted (e.g. a pencil in a glass of water).

When light leaves a denser block into a less dense medium, it bends ______ the normal.

When light leaves a denser block into a less dense medium, it bends away the normal.

True or False? When light travels along the normal (perpendicular to the boundary), it changes direction.

False. Light travelling along the normal passes straight through without bending .

What is the aim of Core Practical 4?

To investigate the refraction of light using transparent rectangular blocks , semi-circular blocks and triangular prisms .

In Core Practical 4, what are the independent and dependent variables?

Independent variable: shape of the block. Dependent variable: direction of refraction.

State two control variables in Core Practical 4.

Width of the light beam and same frequency/wavelength of light across all trials.

What is the ray box used for in Core Practical 4?

To provide a narrow beam of light that can be easily refracted.

To draw the perpendicular (normal) lines accurately and reduce systematic error, students should use a ______ .

To draw the perpendicular (normal) lines accurately and reduce systematic error, students should use a set square .

True or False? It is safe to look directly into the ray box light as long as you stand close to it.

False. Looking directly at the light may damage the eyes — students should avoid looking directly at the light and stand behind the ray box.

Which is more optically dense: diamond ( n ≈ 2.4) or glass ( n ≈ 1.5)?

Diamond . A higher refractive index indicates a more optically dense material.

Since refractive index is a ratio, it has no ______ .

Since refractive index is a ratio, it has no units .

True or False? Diamond has a lower refractive index than glass, so it bends light less.

False. Diamond ( n ≈ 2.4) has a higher refractive index than glass ( n ≈ 1.5), so it bends light more .

What is the aim of the Snell's law core practical?

To investigate the refractive index of glass , using a glass (perspex) block.

In the Snell's law practical, what are the independent and dependent variables?

Independent variable: angle of incidence, i . Dependent variable: angle of refraction, r .

How is the refractive index found from the graph of results in this practical?

Plot sin *i on the *y*-axis against **sin *r on the x -axis. The refractive index is equal to the gradient of the graph.

State one control variable in the Snell's law practical.

Any one of: use of the same perspex block ; width of the light beam ; same frequency/wavelength of light .

Random error in reading the angles can be reduced by using a protractor with a higher ______ .

Random error in reading the angles can be reduced by using a protractor with a higher resolution .

True or False? In the results graph for this practical, the angle of incidence is plotted on the x -axis and the angle of refraction on the y -axis.

False. Sin *i is plotted on the y*-axis and sin *r on the x -axis * — not the raw angles themselves.

Define total internal reflection .

Total internal reflection (TIR) occurs when the angle of incidence is greater than the critical angle and the incident material is denser than the second material, so all of the light is reflected and none is refracted out.

Define critical angle .

The critical angle , c , is the angle of incidence at which the angle of refraction is exactly 90° (the light refracts along the boundary).

State the two conditions needed for total internal reflection to occur.

The angle of incidence is greater than the critical angle . The incident material is denser than the second material.

Give two uses of total internal reflection, each with a named device.

Optical fibres (e.g. endoscopes) and prisms (e.g. periscopes, binoculars, telescopes, cameras).

The larger the refractive index of a material, the ______ the critical angle.

The larger the refractive index of a material, the smaller the critical angle.

True or False? Diamond has a larger critical angle than opal.

False. Diamond ( n ≈ 2.4, c ≈ 25°) has a smaller critical angle than opal ( n ≈ 1.5, c ≈ 42°), since a higher refractive index gives a smaller critical angle .

IGCSEPhysicsEdexcelPhysics (Modular)Unit 2Flashcards5. WavesReflection & Refraction

Reflection & Refraction (Edexcel IGCSE Physics (Modular): Unit 2): Flashcards

Exam code: 4XPH1

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FrontLight & Sound Waves
Define echo.

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Cards in this collection (40)

Define echo.
An echo is the reflection of a sound wave.
Define rarefaction (in a longitudinal wave).
A rarefaction is a region of a longitudinal wave where the lines are drawn further apart, representing lower density/pressure as the wave passes.
How do particles vibrate in a transverse wave such as light, relative to the direction of energy transfer?
In a transverse wave, particles vibrate at right angles (perpendicular) to the direction of energy transfer.
What type of wave is sound?
Sound is a longitudinal wave.
Name two behaviours that both light and sound waves can undergo.
Both light and sound waves can undergo reflection and refraction.
In a longitudinal wave diagram, lines drawn closer together represent ______, while lines drawn further apart represent rarefactions.
In a longitudinal wave diagram, lines drawn closer together represent compressions, while lines drawn further apart represent rarefactions.
True or False?
Light is a longitudinal wave.
False.
Light is a transverse wave (part of the electromagnetic spectrum); sound is the longitudinal wave.
Define reflection (of a wave).
Reflection occurs when a wave hits a boundary between two media and does not pass through, but instead stays in the original medium.
Define refraction (of a wave).
Refraction occurs when a wave passes a boundary between two different transparent media and undergoes a change in direction.
State the law of reflection.
The angle of incidence (i) equals the angle of reflection (r), both measured from the normal.
When light travels from a less dense medium into a more dense medium (e.g. air to glass), which way does it bend relative to the normal?
The light bends towards the normal.
Does the frequency of light change when it refracts? Explain your answer.
No. Frequency does not change during refraction — only speed and wavelength change. This is why light does not change colour when refracted (e.g. a pencil in a glass of water).
When light leaves a denser block into a less dense medium, it bends ______ the normal.
When light leaves a denser block into a less dense medium, it bends away the normal.
True or False?
When light travels along the normal (perpendicular to the boundary), it changes direction.
False.
Light travelling along the normal passes straight through without bending.
What is the aim of Core Practical 4?
To investigate the refraction of light using transparent rectangular blocks, semi-circular blocks and triangular prisms.
In Core Practical 4, what are the independent and dependent variables?
Independent variable: shape of the block.
Dependent variable: direction of refraction.
State two control variables in Core Practical 4.
Width of the light beam and same frequency/wavelength of light across all trials.
What is the ray box used for in Core Practical 4?
To provide a narrow beam of light that can be easily refracted.
What is the resolution of the protractor used in Core Practical 4?
1°.
To draw the perpendicular (normal) lines accurately and reduce systematic error, students should use a ______.
To draw the perpendicular (normal) lines accurately and reduce systematic error, students should use a set square.
True or False?
It is safe to look directly into the ray box light as long as you stand close to it.
False.
Looking directly at the light may damage the eyes — students should avoid looking directly at the light and stand behind the ray box.
Define Snell's law.
Snell's law relates the angles of incidence and refraction to the refractive index of a medium:
$n = \frac{\sin i}{\sin r}$
where n = refractive index, i = angle of incidence (°), r = angle of refraction (°).
Define refractive index.
The refractive index, n, of a material is the ratio of the speed of light in a vacuum to the speed of light in the material:
$n = \frac{speed of light in a vacuum}{speed of light in material}$
It is always greater than 1.
Which is more optically dense: diamond (n ≈ 2.4) or glass (n ≈ 1.5)?
Diamond. A higher refractive index indicates a more optically dense material.
A ray of light enters a glass block of refractive index 1.53, making an angle of incidence of 15° with the normal. Calculate the angle of refraction.
$\sin r = \frac{\sin 15}{1.53} = 0.1692$
$r = \sin^{- 1} (0.1692) = 9.7 \approx 10 °$
Since refractive index is a ratio, it has no ______.
Since refractive index is a ratio, it has no units.
True or False?
Diamond has a lower refractive index than glass, so it bends light less.
False.
Diamond (n ≈ 2.4) has a higher refractive index than glass (n ≈ 1.5), so it bends light more.
What is the aim of the Snell's law core practical?
To investigate the refractive index of glass, using a glass (perspex) block.
In the Snell's law practical, what are the independent and dependent variables?
Independent variable: angle of incidence, i.
Dependent variable: angle of refraction, r.
How is the refractive index found from the graph of results in this practical?
Plot sin *i on the *y*-axis against **sin *r on the x-axis. The refractive index is equal to the gradient of the graph.
State one control variable in the Snell's law practical.
Any one of: use of the same perspex block; width of the light beam; same frequency/wavelength of light.
Random error in reading the angles can be reduced by using a protractor with a higher ______.
Random error in reading the angles can be reduced by using a protractor with a higher resolution.
True or False?
In the results graph for this practical, the angle of incidence is plotted on the x-axis and the angle of refraction on the y-axis.
False.
Sin *i is plotted on the y*-axis and sin *r on the x-axis* — not the raw angles themselves.
Define total internal reflection.
Total internal reflection (TIR) occurs when the angle of incidence is greater than the critical angle and the incident material is denser than the second material, so all of the light is reflected and none is refracted out.
Define critical angle.
The critical angle, c, is the angle of incidence at which the angle of refraction is exactly 90° (the light refracts along the boundary).
State the two conditions needed for total internal reflection to occur.
1. The angle of incidence is greater than the critical angle.
2. The incident material is denser than the second material.
State the equation linking critical angle and refractive index, defining each term.
$\sin c = \frac{1}{n}$
where c = critical angle (°) and n = refractive index.
Give two uses of total internal reflection, each with a named device.
Optical fibres (e.g. endoscopes) and prisms (e.g. periscopes, binoculars, telescopes, cameras).
The larger the refractive index of a material, the ______ the critical angle.
The larger the refractive index of a material, the smaller the critical angle.
True or False?
Diamond has a larger critical angle than opal.
False.
Diamond (n ≈ 2.4, c ≈ 25°) has a smaller critical angle than opal (n ≈ 1.5, c ≈ 42°), since a higher refractive index gives a smaller critical angle.

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