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GCSE Questions - Waves

Q17. The diagram shows Kayjay playing with a remote-controlled car.

(a) The remote control transmits radio waves to the car aerial.

The transmitted radio waves have a frequency of 320 MHz.

Given that the speed of light is 3.0 × 108 m/s, calculate the wavelength of the radio waves.

320 MHz = 3.2 × 108 Hz

Wavespeed = frequency x wavelength

3.0 × 108 = 3.2 × 108 × λ

λ = 3.0 × 108 /3.2 × 108

wavelength = 0.94 metres

[5 marks]

(b) The car aerial is connected to an electrical circuit in the car.

Describe what happens in the electrical circuit when the car aerial absorbs radio waves.

When the energy is absorbed it makes the electrons in the electrical circuitvibrate/oscillate. This means that an alternating current is induced in the electrical circuit with the same frequency as the radio wave.

[2 marks]

(c) The car produces sound waves.

Give two ways in which radio waves are different to sound waves.

Any two from:

radio waves are transverse whereas soundwaves are longitudinal

radio waves travel at a much higher speed than sound waves

radio waves don't need a medium to travel through, but soundwaves cannot travel through a vacuum they have to have a medium to travel through

radio waves are electromagnetic whereas sound waves are mechanical waves

[2 marks]

(Total 9 marks)