Optics Answers

   State the conditions which must be full filled if interference fringes are to be observed where two

 beams of light overlap.

        Explain how it is that these conditions are fulfilled in the interference experiment using two slits, as

        in Young s experiment.

 Draw a labeled diagram of Young's apparatus for producing and observing optical interference.

 Indicate clearly on your diagram the distances that need to be measured to enable yon to determine the wavelength of light

 An essential condition for interference to be observable between wave trains originating from

two sources is that the sources should be coherent. Explain what is meant by coherent in this text.

How did Young achieve this condition in his experiment ? 

 The driver of the stationary car can hear the frequency of the sound either directly from the alarm of the car or from a bridge ahead.

(a.) Name the phenomenon that permits the driver of the stationary car to hear the sound from the bridge.

 (b.) At what frequencies does the driver of the stationary car hear the sounds?

 (c.) The stationary car starts moving towards the bridge at a speed of 6ms~1. At what frequencies does the driver now hears the sounds? Explain why he hears beats and calculate the beat frequency

 (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.