These are similar to one and two mark questions but you will be expected to write in more depth for three and four mark questions.
A microphone connected to an oscilloscope picks up the sound from a siren. The trace produced on the oscilloscope screen is shown below.
Describe how the wave changes as it goes across the screen from left to right. [3 marks]
An Edexcel question courtesy of Pearson Education Ltd.
The amplitude is decreasing , the wavelength is increasing  so the frequency is decreasing .