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State two conditions for an echo to take place
Concept: Characteristics of Sound
Name the phenomenon involved in tunning a radio set to a particular station
Concept: Forced Vibrations
What do you understand by the loudness of sound?
Concept: Characteristics of Sound
In which units is the loudness of sound measured?
Concept: Characteristics of Sound
Draw a graph between displacement and the time for a body executing free/natural vibrations.
Concept: Natural Vibrations
State the safe limit of sound level in terms of decibel for human hearing.
Concept: Characteristics of Sound
Name the characteristic of sound in relation to its waveform
Concept: Reflection of Sound Waves
A person standing between two vertical cliffs and 480 m from the nearest cliff shouts. He hears the first echo after 3s and the second echo 2s later. Calculate:
1)The speed of sound.
2) The distance of the other cliff from the person
Concept: Characteristics of Sound
In the diagram below, A, B, C, D are four pendulums suspended from the same elastic string PQ. The length of A and C are equal to each other while the length of pendulum B is smaller than that of D. Pendulum A is set into a mode of vibrations

1) Name the type of vibrations taking place in pendulums B and D?
2) What is the state of pendulum C?
3) State the reason for the type of vibrations in pendulum B and C.
Concept: Forced Vibrations
Name one property of waves that do not change when the wave passes from one medium to another.
Concept: Characteristics of Sound
The adjacent diagram shows three different modes of vibrations P, Q and R of the same string.

(i) Which vibration will produce a louder sound and why?
(ii) The sound of which string will have maximum shrillness?
(iii) State the ratio of wavelengths of P and R.
Concept: Forced Vibrations
State one important property of waves used for echo depth sounding.
Concept: Characteristics of Sound
Displacement distance graph of two sound waves A and B, travelling in a medium, are as shown in the diagram below.

Study the two sound waves and compare their:
1) Amplitudes
2) Wavelengths
Concept: Reflection of Sound Waves
What do you understand by free vibrations of a body?
Concept: Natural Vibrations
Why does the amplitude of a vibrating body continuously decrease during damped vibrations?
Concept: Damped Vibrations

The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and Bare touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded at the centre) present on the wire flies off when the stem of vibrating tuning fork B is touched to the wooden box but the paper just vibrates when the stem of vibrating tuning fork A is touched to the wooden box.
1) Name the phenomenon when the paper rider just vibrates.
2) Name the phenomenon when the paper rider flies off.
3) Why does the paper rider fly off when the stem of tuning fork B is touched to the box?
Concept: Forced Vibrations
A person is standing at the seashore. An observer on the ship which is anchored in between a vertical cliff and the person on the shore fires a gun. The person on the shore hears two sounds, 2 seconds and 3 seconds after seeing the smoke of the fired gun. If the speed of sound in the air is 320 ms-1 then calculate:
1) the distance between the observer on the ship and the person on the shore.
2) the distance between the cliff and the observer on the ship.

Concept: Characteristics of Sound
When a body vibrates under a periodic force, the vibrations of the body are ______.
Concept: Forced Vibrations
