Refraction
4 marks · NormalA student shines a ray of light at an angle on the surface of water in a tank. Some of the ray is reflected and some is refracted. The diagram shows the ray and the normal.
Use the diagram to answer the following.
Which ray shows reflection? Which shows refraction? Write their labels.
Describe the difference between reflection and refraction using this example.
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) BC is reflection; BD is refraction. · must show BC = reflected ray, BD = refracted ray
(b) Reflection is when the light bounces back from the surface at the same angle as it arrived (angle of incidence = angle of reflection). Refraction is when some light passes into the water and changes direction (bends) because its speed changes. · must show Reflection: light returns into air, angle of incidence = angle of reflection, Refraction: light enters water and bends due to change in speed
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies BC as reflection (reflected ray)
B1 (a) · 1 mark · Identifies BD as refraction (refracted ray)
B1 (b) · 2 marks · Describes reflection as light bouncing off at equal angle; describes refraction as light entering and changing direction (bending) because of speed change
Worked solution
a) BC is the reflected ray; BD is the refracted ray. b) In reflection, the light bounces off the surface at the same angle as it arrived. In refraction, the light passes into the new medium (water), changes speed, and bends.