GCSE Questions: Waves

Q2. A radar gun can be used to measure the speed of a car.
Microwaves are emitted by the radar gun and reflected by the car, as shown in the diagram.

(a) The microwaves reflected by the moving car have a different frequency from the microwaves emitted by the radar gun.

What is the name of the effect causing this change in frequency?

[1 mark]

(b) The data in the table below are measurements taken from three different cars on the same piece of road.

Car
Frequency of
emitted microwaves
in kHz
Frequency
of reflected
microwaves in kHz
A
27 000 000
27 000 002
B
27 000 000
27 000 000
C
27 000 000
26 999 997


(b)

(i) State which car in the table is moving towards the radar gun. Give a reason for your answer.

[2 marks]

(ii) State which car in the table is moving the fastest. Give a reason for your answer.

[2 marks]

(Total: 5 marks)