(a) The new Tetra communications system to be used by the police transmits digital signals using microwaves of wavelength 75 cm.

The signals travel through the air at 300 000 000 m/s.

(i) What is a digital signal?

(1 marks)

(ii) Calculate the frequency of the microwaves used by the Tetra system. Show clearly how you work out your answer.

Frequency = ....................................... hertz
(1 mark)

(b) Read the following extract from a newspaper and then answer the questions that follow.

"Residents of Stag Hill Court, a luxury block of flats, are shocked at the plans to site a mobile phone mast on the roof of the flats. They oppose the mast on health grounds, quoting research in Germany that has found a possible increase in cases of cancer around mobile phone masts.

A spokesperson for the telecoms company said, ‘The residents should not worry. The research carried out by our own scientists has found no link between ill health and mobile phone masts’.

This has not reassured the residents, who argue that new independent research is urgently needed."

(i) Explain why living near a mobile phone mast could cause ill health.

(3 marks)

(ii) Suggest two reasons why the residents have not been reassured by the research carried out by the telecoms company.

(2 mark)

How did you do? Click to show the mark scheme

From Q5 P1 AQA June 2007