Refraction, Reflection & Polarisation (Edexcel International A Level Physics)

The refractive index of glass varies with the colour of light.

refractive index of glass for red light = 1.513

refractive index of glass for violet light = 1.532

A ray of white light is incident on side AB of a rectangular glass block, as shown.

The red light and violet light from the incident ray arrive at slightly different points on side CD.

Determine the distance between these points.

Distance between points = ........................(5)

White light is incident on a boundary between glass and air, as shown.

Explain what happens to the red light and the violet light when meeting the boundary.

Your answer should include calculations.

When unpolarised light passes through a polarising filter, the light becomes plane polarised.

Explain the difference between unpolarised and plane polarized light.

An unpolarised light source is directed towards a screen. The intensity of radiation measured at the screen is 1.00 W m⁻².

Two polarising filters are placed between the light source and the screen.

Initially there is an angle of 0° between their planes of polarisation, as shown.

One of the polarising filters is then rotated, as shown.

Sketch a graph to show how the intensity of light measured at the screen varies as the filter is rotated from 0° to 90°.

Polarisation can be used to identify when some materials are under stress. Placing the material under stress causes the plane of polarisation of the light passing through the material to be rotated. The greater the stress, the greater the rotation of the plane of polarisation of the light.

A piece of transparent material under stress is positioned between two polarizing filters. There is an angle of 90o between the planes of polarisation of the two polarising filters.

Explain how this photograph can be used to identify areas of the material with different amounts of stress.

Light is a transverse wave.

Describe the difference between transverse waves and longitudinal waves.

Two prisms, A and B, made from different types of glass are placed in contact as shown. An incident ray of light enters prism A.

i) State why the incident ray of light does not change direction as it enters prism A.

(1)

ii) The refractive index of the glass in prism B is greater than the refractive index of the glass in prism A. When the ray of light reaches the boundary between the prisms, some light is reflected and some is refracted.

Complete the diagram to show the two paths taken by the reflected and refracted light until they have returned to the air.

(4)

iii) Calculate the angle of refraction as this ray of light travels across the boundary between prism A and prism B.

refractive index of glass in prism A = 1.40

refractive index of glass in prism B = 1.55

Angle of refraction = .............................(3)

The light emerging from prism B is observed through a polarising filter. The polarizing filter is rotated gradually, and the light transmitted by the filter varies in intensity.

Explain how this observation demonstrates that light waves are transverse.