Optics Answers

  (i.) What is meant by Doppler's effect?

  (ii.) A bat flies at a steady speed of 5ms^-1 and emits waves of frequency 85.0kHz. What is the

       frequency of the wave detected by the bat after reflection from a stationary obstacle directly ahead of the bat?

A stationary observer hears beats when a source of sound of frequency 100Hz moves directly away from the observer with a speed of 10.0ms^-1 towards a vertical wall. Explain why beats are produced and calculate the beat frequency

State the principle of superposition of waves. 

How is this principle observed in the formation of maxima and minima of a typical diffraction pattern

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

diagram, procedure, precautions, observations and conclusions

Distinguish between transverse and longitudinal waves.

The speed of sound in air is 341ms^-1 at a temperature of 290K and a pressure of1.00×10⁵Pa. If

the temperature falls to 285K and the pressure of1.02×10⁵Pa, does the speed of sound increase

  or decrease? Justify your statement.

What would be the effect of such a change of atmospheric conditions on the frequency of sound

emitted by an organ pipe?

A source of sound frequency 550Hz emits waves of wavelength 600 mm in air at 20°C. What is the

velocity of sound in air at this temperature? What will be the wavelength of the sound from this source in air at 0°C?

(a.) Beats are heard when a tuning fork and a sonometer wire vibrate simultaneously with

frequencies f1 and f2 respectively, f2 being slightly different from f1.

(b.) In an arrangement such as that described in (a), a sonometer wire vibrates under a constant

tension in its fundamental mode and two beats per second are heard when f1 = 512Hz. When the

length of the wire is increased by 2mm, beats are no longer heard. Calculate, to three significant

figures,

(i.) The initial frequency of vibration.

(ii.) The initial length of the wire. 

(a.) Beats are heard when a tuning fork and a sonometer wire vibrate simultaneously with

frequencies f1 and f2 respectively, f2 being slightly different from f1.

(i.) Explain what is meant by the term beats and explain how they are formed.

(ii.) Show that the beat frequency is equal to the difference between fi and f2·

When a tuning fork of frequency 256//z is sounded together with a sonometer wire emitting its

      fundamental frequency, 6 beats are heard every second. When the prongs of the tuning fork are

       highly loaded, 4 beats are heard every second.

      (a.) What is the fundamental frequency of the sonometer wire?

(b.) If the length of the sonometer wire is 25cm, and the mass per unit length of the material of the

wire is 9.0 ×10-3kgm¯¹, calculate the tension in the sonometer wire.