Refraction
4 marks · NormalThe diagram shows the direction of a wave as it passes from shallow water into deep water at an angle. The wave changes speed and is refracted.
Describe what happens to the speed and direction of the wave as it passes from shallow to deep water.
Explain why the direction of the wavefront changes.
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(a) The speed of the wave increases and the wave bends away from the normal. · must show States speed increases, States wave bends away from the normal
(b) The direction of the wavefront changes because the wave speed changes as it enters a different medium (deeper water), causing one side of the wave to move faster than the other. · must show Reference to change in speed causing refraction, Explanation involving parts of the wavefront moving at different speeds
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Marking points
B1 (a) · 1 mark · States that the speed increases as the wave moves to deeper water
B1 (a) · 1 mark · States that the wave bends away from the normal
B1 (b) · 2 marks · Explains that a change in speed at the boundary results in refraction; describes how one part of the wavefront changes speed before the other, causing a change in direction
Worked solution
a) The wave speed increases as it moves from shallow to deep water, and the wave bends away from the normal. b) The wavefront changes direction because waves travel faster in deeper water. As part of the wavefront enters deep water first, it speeds up, causing the wave to bend and change direction (refraction).