Question

er stands on a bridge over the N142 motorway at night. A police car travels effec- tively directly towards the observer at a speed of 112 kmh-1, with his horn sounding at a frequency of 250 Hz. (a) Calculate the frequency heard by the observer. 1 mark (b) The cars blue lights are flashing. Taking a typical value for the frequency of blue light, 2 marks calculate the frequency of the light seen by the observer. (c) The car approaches a tunnel in a vertical cliff. The horn's sound reflects off the clif 2 marks face and the echo is heard by the driver. What frequency does the driver hear?

Answer 1