Practise EM waves: refraction and absorption. 20 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
The student then shines a ray of light at the block along the normal (angle of incidence 0°). Describe what happens to the direction of the ray as it enters the glass.
It continues in the same direction.
What happens to the frequency of the light as it enters the glass?
It stays the same.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy3 marks
A ray of light travels from air into a glass block.
(a) What happens to the speed and the wavelength of the light as it enters the glass? Tick (✓) one box.[1]
Both decrease
Both increase
Speed decreases, wavelength increases
Speed increases, wavelength decreases
(b) What happens to the frequency of the light as it enters the glass?[1]
(c) The ray meets the glass surface along the normal (angle of incidence 0°). Does the ray change direction as it enters the glass?[1]
Show the answer and mark scheme
(a)Answer: Both decrease
(b)Answer: It stays the same.
it stays the same (does not change)
(c)Answer: No, it continues in the same direction.
no, it carries straight on
Question 2Medium6 marks
A student shines a ray of red light from air into a glass block. The ray meets the surface of the block at an angle of incidence of 40°.
(a) Explain why the ray changes direction as it enters the glass.[2]
(b) The frequency of the light does not change when it enters the glass. What happens to the wavelength of the light? Give a reason for your answer.[2]
(c) The student then shines a ray of light at the block along the normal (angle of incidence 0°). Describe what happens to the direction of the ray as it enters the glass.[1]
(d) The student repeats the experiment with blue light at the same angle of incidence. The blue light is refracted by a slightly different amount from the red light. Suggest why.[1]
Show the answer and mark scheme
(a)Answer: The light slows down as it enters the glass; because it arrives at an angle, it is refracted.
light travels more slowly in glass than in air / its speed changes at the boundary
so it is refracted (towards the normal) because it meets the boundary at an angle
(b)Answer: It decreases, because the speed decreases while the frequency stays the same (v = f λ).
the wavelength decreases
wave speed = frequency × wavelength, so if the speed decreases at constant frequency, the wavelength must decrease
(c)Answer: It continues in the same direction.
it does not change direction / carries straight on
(d)Answer: Blue and red light travel at slightly different speeds in glass.
blue light travels at a (slightly) different speed in glass from red light
Question 3Hard6 marks
A student has two identical empty metal cans. One can is painted matt black and the other is covered with shiny silver foil. The student also has a radiant heater, two thermometers, a measuring cylinder, a stopwatch and a supply of cold water.
Plan an investigation to compare how much infrared radiation is absorbed by the matt black surface and by the shiny silver surface.[6]
Show the answer and mark scheme
Answer: Level-of-response answer: equal volumes of water at the same starting temperature in each can, cans equidistant from the heater, measure the temperature rise of each over the same time; the larger rise shows the better absorber.
use the measuring cylinder to put the same volume of water in each can
the water in both cans starts at the same temperature
place the cans the same distance from the radiant heater (e.g. one on each side)
measure the starting temperature of the water in each can with a thermometer
switch on the heater and measure the temperature in each can at regular intervals (e.g. every minute for 10 minutes)
compare the temperature rises: the larger temperature rise shows the better absorber
use lids and stand the cans on an insulating mat to reduce other energy transfers
repeat the investigation and calculate a mean temperature rise
safety: the heater becomes very hot; do not touch it and let it cool before moving it
Marked with levels of response: the full level descriptors are in the app.