1. What sort of wave does your system use? What is an approximate wavelength of this wave?

Radio waves, with a wavelength ranging from 2.7mm to 100m.

2. What sort of distance is it usually used to measure? What sort of length would you expect the distance to be?

The distance to an object within the radio horizon. This width is given by the formula:

${\displaystyle \mathrm {horizon} _{\mathrm {km} }=3.569\times {\sqrt {\mathrm {height} _{\mathrm {metres} }}}.}$

So, a radar 10m above the Earth's surface has a range of 11.3 km.

3. Why is measuring this distance useful to society?

e.g. Radar is used at airports to locate aeroplanes and co-ordinate them so that they can land safely, avoiding collisions.

4. Draw a labelled diagram of your system.

5. Explain how the system works, and what data are collected.

The 'dish' rotates, and the transmitter on it transmits a pulse of radio waves. The waves, if they hit an aircraft, are reflected by it. The dish reflects the reflected radio pulse onto a receiver (allowing for some variety in incoming angles due to varying distances of aircraft). The time taken for the signal to travel to the aircraft and back is recorded, and the speed of the radio pulse (3 x 108ms−1) is already known.

6. Explain how the distance to the object is calculated using the data collected.

${\displaystyle v={\frac {s}{t}}}$

${\displaystyle s=tv\,}$,

where s = distance, t = time and v = velocity. In this case, the time taken to travel to the aircraft t is half of the total time taken to travel to the aircraft and back T, so:

${\displaystyle s={\frac {Tv}{2}}}$

7. What limitations does your system have? (e.g. accuracy, consistency)

• Random noise e.g. birds, weather