Properties of Waves
5 marks · NormalThe diagram shows a ray of light entering a glass block from air at an angle.
The angle between the incident ray and the normal is 35°.
Name the phenomenon shown by the light ray at the air-glass boundary and explain what causes it to occur.
Describe what happens to the speed and direction of the light ray as it enters the glass.
Draw and label on the diagram: - the angle of incidence - the angle of refraction.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Refraction. It occurs because light changes speed when passing from air to glass. · must show refraction definition, cause: speed change
(b) The light ray slows down and bends towards the normal as it enters the glass. · must show decrease in speed, change in direction
(c) The angle of incidence is between incident ray and normal; the angle of refraction is between refracted ray and normal, drawn in diagram. · must show correctly marked angles
Must show: angle of incidence, angle of refraction
Common mistakes: Calling refraction reflection; Wrong direction of bending
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies the phenomenon as refraction.
B2 (a) · 1 mark · States it occurs because of the change of speed as light enters glass.
B3 (b) · 1 mark · States the light slows down in glass (or travels slower in glass than air).
B4 (b) · 1 mark · States the ray bends towards the normal.
B5 (c) · 1 mark · Correctly draws and labels the angle of incidence and angle of refraction.
Worked solution
a) The phenomenon is refraction. Refraction occurs because the speed of light changes when it passes from one medium (air) to another (glass).
b) The light ray slows down when entering glass and bends towards the normal.
Angles shown and labeled as required.