Optics Answers

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 source of sound of frequency 2500Hz is placed in front of a flat wall. If the microphone is moved

from the source directly towards the wall, a series of minimum values in its output is observed at

equally spaced points.

Why does this effect does occur? Calculate the separation of these points if the speed of sound in air

at this temperature is 330ms-1.

(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. 

(i.) The velocity v of a transverse wave on a stretched string is given by V = sqrt(T/µ) where T is the tension and µ is the mass per unit length.

      (a.) Show that the equation is dimensionally correct.

      (b.) Derive an expression for the fundamental frequency of a vibrating wire.

A clock pendulum has a period of 2.00s. A simple pendulum setup in front of it gains on the clock so

      that the two vibrate in phase at intervals of 22.0s. Calculate:

      (a.) the period of the simple pendulum

      (b.) the fractional change in length of the simple pendulum necessary for the two periods to be

      equal.