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Superposition of waves
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Speed of Sound

20) factors affecting the velocity of sound in the gas:

5) At 00C velocity of sound in dry air = 332 m/sec, while the velocity sound in water is 1440 m/sec. At t0 C the velocity of sound will be (for low values of t, t/273<<1).

Vt = 330+0.61 m/sec.

6) In atomic weights of two gases are M1 and M2 respectively then

21) features of musical sound:

1) Loudness:

The quality of sound on the basis of which sound is said to be high or low. It depends on the.

a)      shape of the source

b)      intensity of sound

unit of L is “phone” when I is measured in decibel.

The amplitude of a roaring lion is more than sound produced by a mosquito.

2) Pitch:

On the basis of this characteristic sound is said to be sharp or dull. Pitch increases with the frequency of sound. For example pitch of roaring lion is less than that of sound of mosquito.

3) Quality:

On the basis of this property the sound of same loudness and pitch can be differentiated. The basis of this differentiation is number of harmonics present in the sound, relative intensity etc. On increasing the number of overtones, sweetness of sound increases. Example: Whistle’s sound (closed pipe) is less sweet than that of flute (open pipe)

22) some important information:

1) Shock waves: A body moving with a supersonic velocity leaves behind itself a conical disturbance region. Disturbance of this kind is called a short wave. These have a large amount of energy which can damage the buildings.

2) Frequency of infrasonic waves is less than 20 Hz.

3) Frequency of ultrasonic waves is more than 20000 Hz.

4) Mach number = speed of any vehicle or body/ speed of sound.

5) Vibration of tuning fork: when tuning fork is sounded by striking its one end on rubber pad, then

(a)   The ends of prongs vibrate in and out while the stem vibrates up and down or        vibrations of the prongs are transverse and that of the stem is longitudinal.   Generally tuning fork produces fundamental node.

(b)   At the free end of a fork antinodes are formed. At the place where stem is fixed antinodes is formed. In between these antinodes, nodes are formed.

Fig (7)

(c)   Frequency of tuning fork :

t = thickness of tuning fork.

l = length of arm of fork.

E = Coefficient of elasticity for the material of fork.

d = density of the material of a fork.

(d) Frequency of tuning fork decrease with increase in temperature.

(e) Increasing the weight, the frequency of a tuning fork decreases while on filing the prongs near stem, the frequency decreases.

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