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Use the formula v= sqrt((gamma p)/(rho))...

Use the formula `v= sqrt((gamma p)/(rho))` to explain why the speed of sound in air
(a) is independent of pressure.
(b) increases with temperature.
(c ) increases with humidity

Text Solution

Verified by Experts

Assume ideal gas law `p = (rho RT)/(M)`, where `rho` is the density, M is the molecular mass, and T is the temperature of the gas. This gives `v= sqrt((gamma RT)/(M))`. This shows that v is :
(a) Independent of pressure
(b) Increases as `sqrtT`
(c ) The molecular mass of water (18) is less than that of `N_(2) (28) and O_(2) (32)`
Therefore as humidity increases, the effective molecular mass of air decreases and hence v increases.
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Knowledge Check

  • On increasing the temperature, the speed of sound in air:

    A
    increase
    B
    decrease
    C
    no change
    D
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    C
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    D
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  • Root mean square speed of the molecules of ideal gas is V. If pressure is increased two times at constant temperature , then the rms speed will become:

    A
    V
    B
    4V
    C
    `V/2`
    D
    2V
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