Question 44: Oscillations

Question

A student performed the experiment to measure the speed of sound in air using resonance air-column method. Two resonances in the air-column were obtained by lowering the water level. The resonance with the shorter air-column is the first resonance and that with the longer air-column is the second resonance. Then,

Accepted Answer

The sharpness of resonance decreases with increasing column length.
The first resonance happens when length of air column $$\approx$$ $$\lambda/2$$. The prongs of the tuning fork are always kept in a vertical plane and amplitude of vibration is typically in the mm range.
From the figure, we have
$${\lambda  \over 4} = {l_1} + e$$
where e is the end-correction. Therefore,
$${l_1} + \left( {{\lambda  \over 4} - e} \right) < {\lambda  \over 4}$$

Answer

the intensity of the sound heard at the first resonance was more than that at the second resonance.

Answer

the prongs of the tuning fork were kept in a horizontal plane above the resonance tube.

Answer

the amplitude of vibration of the ends of the prongs is typically around 1 cm.

Answer

the length of the air-column at the first resonance was somewhat shorter than 1/4th of the wavelength of the sound in air.

Oscillations

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