Question

(a) : 1. What is the principle on which SONAR is based. 

2. An observer stands at a certain distance away from a cliff and produces a loud sound. He hears the echo of the sound after 1.8 s. Calculate the distance between the cliff and the observer if the velocity of sound in air is 340ms^-1. 

(b) : A vibrating tuning fork is placed over the mouth of a burette filled with water: The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column. 

1. Name the phenomenon taking place when this happens. 

2. Why does the sound become very loud for this length of the water column? 

(c) : 

1. What is meant by the terms (a) amplitude (b) frequency of a wave? 

2. Explain why stringed musical instruments, like the guitar, are provided with a hollow box. 

Answer 1

(a) :

1. SONAR is based on Echo of Sound. 

2. Distance between cliff and source of sound

(b) : 

1. The phenomenon is called ‘resonance of sound’. 

2. A some particular length of air column the natural frequency of air column corresponds the frequency of tuning fork. At this moment the sound waves reinforce to produce loud sound. 

(c) : 

1. The maximum displacement of vibrating particle about its mean position is called its amplitude. The number of waves which pass through a point in a medium in one second is called frequency. 

2. Stringed musical instruments are provided with hollow box so that when the vibrations are produced by strings are impressed on the enclosed air, they produced forced vibrations and a loud sound is produced.