Waves
4 marks · EasyLook at the diagram below showing a ray of light travelling from air into a glass block at 30° to the normal.
State the meaning of 'refraction'.
Draw an arrow on the diagram to show the path of the refracted ray inside the glass block, bending towards the normal.
Explain why the refracted ray bends towards the normal.
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 is the bending of a wave as it passes from one medium to another.
(b) Arrow drawn showing ray bending towards the normal inside glass. · must show Ray inside bends towards normal
(c) The ray slows down in glass (denser medium), causing it to bend towards the normal.
Must show: Refracted ray correctly shown closer to normal inside the glass block
Common mistakes: Ray not drawn bending correctly; Confusing refraction with reflection
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Defines refraction correctly as bending of waves at a boundary.
B2 (b) · 1 mark · Draws arrow on diagram showing refracted ray bending towards the normal.
B3 (c) · 1 mark · States that the ray slows down in glass/more optically dense medium.
B4 (c) · 1 mark · Links slowing down to bending towards the normal.
Worked solution
a) Refraction is the bending of a wave when it passes from one medium to another.
b) The refracted ray inside the glass should be drawn at a smaller angle to the normal than the incident ray (bends towards the normal).
c) The light ray bends towards the normal because it slows down as it enters the denser glass from air.