Short Answer Typei) What is the principle on which SONAR is based?
ii) 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 340 m/s.i) Principle of SONAR is based on echo.
Echo is a reflection of the sound that arrives at the listener with a delay after the direct sound.
ii) Given,
Velocity of the sound, v = 340 m/s;
Time after which the sound is heard, t = 1.8 sec
Distance travelled by sound = 2d
Distance = Speed x time
2d = v
This implies, 
= 
= 170 x 
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.
i) Name the phenomenon taking place when this happens.
ii) Why does the sound become very loud for this length of water column?Calculate the equivalent resistance between the points A and B for the following combination of resistors, 
A metal wire of resistance 6 is stretched so that its length is increased to twice its original length. Calculate its new resistance.
You have been provided with a solenoid AB.
i) What is the polarity at end A.
ii) Give one advantage of an electromagnet over a permanent magnet.i) It is observed that the temperature of the surroundings starts falling when the ice in a frozen lake starts melting. Give a reason for the observation.
ii) How is the heat capacity of the body related to its specific heat capacity?
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