Refraction is the change in direction of light as it passes a boundary between two different transparent media, caused by a change in speed.

Which properties of light change when it undergoes refraction?

Speed and wavelength change; the frequency does not change.

When light passes from air into glass, it bends .......... the normal.

When light passes from air into glass, it bends towards the normal.

In the refraction experiment, what does the gradient of a graph of sin θ 2 against sin θ 1 represent?

The gradient equals the refractive index , n , of the block.

True or False? The refractive index of a material is always less than 1.

False. Since light always travels slower in a medium than in a vacuum, v < c , so n = c / v is always greater than 1 .

Why is a laser preferred over a ray box (lightbox) when investigating refraction?

A laser produces a more concentrated, well-defined ray , reducing the uncertainty when tracing the light path.

Define the critical angle ( C ).

The critical angle is the angle of incidence at which the angle of refraction is exactly 90° , so the refracted ray travels along the boundary.

What are the two conditions required for total internal reflection to occur?

The angle of incidence θ 1 must be greater than the critical angle, C The refractive index of the first medium n 1 must be greater than the refractive index of the second medium n 2

At the critical angle, the angle of refraction is exactly .......... .

At the critical angle, the angle of refraction is exactly 90° .

True or False? Total internal reflection can occur when light travels from a less optically dense medium into a more optically dense medium.

False. TIR requires light to travel from a medium of higher refractive index ( n 1 ) into one of lower refractive index ( n 2 ), for example from glass into air.

Which four wave phenomena are unique to waves and do not occur for particles?

Reflection , refraction , polarisation and diffraction .

State the key relationship between the angle of incidence and the angle of reflection.

The angle of incidence i is equal to the angle of reflection r .

Define polarisation .

Polarisation is a wave phenomenon, occurring only in transverse waves , in which vibrations are restricted to a single direction.

Diffraction is the spreading out of waves when they pass an obstruction, such as a narrow slit (an aperture ).

Which property of a wave changes when it is diffracted, and why?

Its amplitude decreases, because some energy is dissipated as the wave passes through the gap.

Diffraction effects are most noticeable when the gap size is approximately the same as, or smaller than, the .......... of the wave.

Diffraction effects are most noticeable when the gap size is approximately the same as, or smaller than, the wavelength of the wave.

For a single slit, how does the diffraction pattern of white light differ from that of blue laser light?

With white light, the central maximum is white ; all other maxima are spread into a spectrum , with violet/blue nearest to the centre and red furthest away, and the fringe spacing is smaller with wider maxima.

True or False? During refraction of white light through a prism, red light is refracted (bent) more than violet light.

False. Violet light is slowed down more than red light and is therefore refracted more.

A LevelPhysicsOCRFlashcards4. Electrons, Waves & PhotonsRefraction & Reflection

Refraction & Reflection (OCR A Level Physics): Flashcards

Exam code: H556

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Define refraction.

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Cards in this collection (21)

Define refraction.
Refraction is the change in direction of light as it passes a boundary between two different transparent media, caused by a change in speed.
Define refractive index (n).
$n = \frac{c}{v}$
where c is the speed of light in a vacuum and v is the speed of light in the medium.
Which properties of light change when it undergoes refraction?
Speed and wavelength change; the frequency does not change.
State Snell's law.
$n_{1} \sin θ_{1} = n_{2} \sin θ_{2}$
where θ₁ and θ₂ are the angles of incidence and refraction, measured from the normal.
When light passes from air into glass, it bends .......... the normal.
When light passes from air into glass, it bends towards the normal.
In the refraction experiment, what does the gradient of a graph of sin θ₂ against sin θ₁ represent?
The gradient equals the refractive index, n, of the block.
True or False?
The refractive index of a material is always less than 1.
False.
Since light always travels slower in a medium than in a vacuum, v < c, so n = c/v is always greater than 1.
Why is a laser preferred over a ray box (lightbox) when investigating refraction?
A laser produces a more concentrated, well-defined ray, reducing the uncertainty when tracing the light path.
Define the critical angle (C).
The critical angle is the angle of incidence at which the angle of refraction is exactly 90°, so the refracted ray travels along the boundary.
What are the two conditions required for total internal reflection to occur?
1. The angle of incidence θ₁ must be greater than the critical angle, C
2. The refractive index of the first medium n₁ must be greater than the refractive index of the second medium n₂
How is the critical angle formula derived from Snell's law?
Snell's law: $n_{1} \sin θ_{1} = n_{2} \sin θ_{2}$
At the critical angle, θ₁ = C and θ₂ = 90°, so:
$n_{1} \sin C = n_{2}$
$\sin C = \frac{n_{2}}{n_{1}}$
At the critical angle, the angle of refraction is exactly ...........
At the critical angle, the angle of refraction is exactly 90°.
True or False?
Total internal reflection can occur when light travels from a less optically dense medium into a more optically dense medium.
False.
TIR requires light to travel from a medium of higher refractive index (n₁) into one of lower refractive index (n₂), for example from glass into air.
Which four wave phenomena are unique to waves and do not occur for particles?
Reflection, refraction, polarisation and diffraction.
State the key relationship between the angle of incidence and the angle of reflection.
The angle of incidence i is equal to the angle of reflection r.
Define polarisation.
Polarisation is a wave phenomenon, occurring only in transverse waves, in which vibrations are restricted to a single direction.
Define diffraction.
Diffraction is the spreading out of waves when they pass an obstruction, such as a narrow slit (an aperture).
Which property of a wave changes when it is diffracted, and why?
Its amplitude decreases, because some energy is dissipated as the wave passes through the gap.
Diffraction effects are most noticeable when the gap size is approximately the same as, or smaller than, the .......... of the wave.
Diffraction effects are most noticeable when the gap size is approximately the same as, or smaller than, the wavelength of the wave.
For a single slit, how does the diffraction pattern of white light differ from that of blue laser light?
With white light, the central maximum is white; all other maxima are spread into a spectrum, with violet/blue nearest to the centre and red furthest away, and the fringe spacing is smaller with wider maxima.
True or False?
During refraction of white light through a prism, red light is refracted (bent) more than violet light.
False.
Violet light is slowed down more than red light and is therefore refracted more.

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