Refraction
3 marks · EasyThe diagram shows a light ray entering a glass block from air at an angle to the normal.
On the diagram below, draw and label:
the normal at the point where the ray enters the glass
the angle of incidence
What happens to the speed of light as it passes from air into glass?
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.
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(a) — · must show Normal line at right angles to the surface at entry point, Angle of incidence labeled between incoming ray and normal
(b) The speed of light decreases as it passes from air into glass.
Must show: Normal is drawn at right angles to surface at entry point, Angle of incidence is clearly labeled between incident ray and normal, Speed decreases in glass
Common mistakes: Incorrectly labeling angle of refraction instead of angle of incidence; Drawing normal at wrong place; Saying speed increases
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Normal correctly drawn at right angle to surface at entry point.
B2 (a) · 1 mark · Arrow/angle of incidence correctly labeled between incident ray and normal.
B3 (b) · 1 mark · States speed of light decreases in glass.
Worked solution
a) The normal should be drawn at 90° to the surface where the ray meets the glass; the angle between the incoming ray and the normal is the angle of incidence.
b) The speed of light decreases as it enters glass from air.