Optics Answers

 (a.) Explain the term Doppler effect.

  A car sounding an alarm of frequency 512Hz is approaching a stationary car at a speed of 10ms^-1

 (b.) Explain why the driver of the stationary car has the impression that the frequency of the sound is

    increasing.

 An observer travelling with a constant velocity of 25ms-1 passes close to a stationary source and notices that there is a change of frequency of 60Hz as he passes the source. What is the

           frequency of the source? 

Distinguish between transverse and longitudinal waves.

Describe an experiment to determine the speed of sound in free air from measurements of frequency and wavelength using progressive wave. Your account should include a diagram, procedure, precautions, observations and conclusions.

As an ambulance sounding a siren approaches a control point, the frequency of the siren is measured to be 360 Hz and as it passes and moves away, the frequency is presumed to be 320Hz.

 Explain why there is a difference and calculate the speed of the ambulance and the overall Doppler

shift that occurs

Describe an experiment to determine the speed of sound in free air. Your account should include

          a diagram, procedure, precautions, observations and conclusions.

Use examples to explain why and how waves are classified.

(a.) A motorcyclist travels at a constant speed of 72 km/h along a straight level road towards an

observer standing at the center of the bridge over the road. When the motor-cyclist is distant, the

observer hears a sound of frequency 65,0 //z from the engine of the motorcycle. 

(b.) A second motor-cyclist now rides along-side the one mentioned in (b), at the same constant

speed of 72 km/h. The frequency of the sound of the second motorcycle is lower than that of the

first motorcycle. When the two machines are traveling towards the observer, from the same

direction, the intensity of the sound received varies with a frequency of 3.0 Hz.

Name the effect causing the variation of sound intensity and explain how it arises in this case. What

would be the frequency of the variation of sound intensity after the motor-cycles have passed under

the bridge and are moving away from the observer?

A motor-cyclist travels at a constant speed of 72 kmh^-1 along a straight tevel road towards an

observer standing at the center of the bridge over the road. When the motor- cyclist is distant, the

observer hears a sound of frequency 65,0 Hz from the engine of the motor-cycle. What would be

the frequency of the sound heard by the observer after the motor cycle has passed under the bridge

and is along way from the observer?

Describe a simple laboratory demonstration of the Doppler Effect for sound waves.