Refraction
4 marks · NormalThe diagram below shows a wavefront striking a flat barrier at an angle.
Mark and label the angle of incidence on the diagram.
State the law of reflection.
If the angle of incidence is , what is the angle of reflection?
Explain why the reflected wave leaves the barrier at this angle.
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) The angle of incidence should be marked between the incident wavefront (approaching) and the normal (the dashed line), and labelled appropriately. · must show Angle between incident ray and normal marked, Labelled as angle of incidence
(b) The angle of incidence equals the angle of reflection. · must show States law of reflection
(c) 30 degrees
(d) Because the law of reflection says these angles are always equal. · must show Reference to law of reflection
Common mistakes: Confusing the incident and reflected angle; Not measuring from the normal
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Angle of incidence correctly marked from normal and labelled
B1 (b) · 1 mark · States the law of reflection correctly
A1 (c) · 1 mark · Correct angle of reflection given as 30°
B1 (d) · 1 mark · Correct explanation relating to law of reflection
Worked solution
(a) Mark an angle from the incident wavefront line to the normal at the point where the wave meets the barrier, and label it 'angle of incidence'.
(b) Law: The angle of incidence = angle of reflection.
(c) The angle of reflection is also 30°.
(d) This is because the law of reflection states that these angles are always equal.