Question

A simple instrument used to produce pure sound of fixed frequency is-
(A) a tuning fork
(B) fire tongs
(C) simple pendulum
(D) metre scale

Answer 1

Hint:Sound can be produced by anything like clapping our hands or banging the utensil with a stick. Whatever sound is produced it has its own characteristics like frequency, wavelength, pitch or the speed with which it propagates through the given medium.

Complete step by step answer:
We are provided with four options. Let us analyse them. A metre scale is an instrument used to measure lengths. It does not produce any sound, so it cannot be the correct option. Simple pendulum is a name given to a system in which a bob of some mass tied to a thread or a string fixed at some point and when displaced from its equilibrium position it undergoes to and fro motion. It is used in experiments to determine the value of acceleration due to gravity but it does not produce sound of a fixed frequency.Now we see a tuning fork. It vibrates at a set frequency after being struck on the heel of the hand and is used to assess vibratory sensation. The important characteristic of the sound produced by it is that it is of fixed frequency.
Hence tuning fork is the correct option. So, the correct option is (A).

Note:The frequency is the characteristic of the source which produces the sound. It does not change as the wave propagates through a medium or if it travels from one medium to another.