Refraction
2 marks · EasyA ray of light passes from air into water. Explain why the ray changes direction at the boundary between the two media.
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The ray changes direction because light travels at different speeds in air and in water. The change in speed causes the light to bend at the boundary between the two media.
Also accept: Light slows down as it enters water from air, causing it to bend.; Because light travels at a different speed in water than in air, it refracts.
Common mistakes: Saying the ray changes direction because it is reflected.
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Marking points
B1 · 1 mark · States or implies light changes speed at boundary.
B2 · 1 mark · Links the change of speed to the ray bending/changing direction (refraction).
Worked solution
Light changes speed when it moves from air into water. Because of this change in speed, the light ray bends at the boundary, which is called refraction.