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,

• A. the intensity of the sound heard at the first resonance was more than that at the second resonance
• B. the prongs of the tuning fork were kept in a horizontal plane above the resonance tube
• C. the amplitude of vibration of the ends of the prongs is typically around 1 cm
• D. the length of the air-column at the first resonance was somewhat shorter than 1/4th of the wavelength of the sound in air

Answer 1

Answer: (A), (D)

The correct options are
A the intensity of the sound heard at the first resonance was more than that at the second resonance
D the length of the air-column at the first resonance was somewhat shorter than 1/4th of the wavelength of the sound in air

Larger the length of air column, feebler is the intensity.

For closed pipe, the fundamental frequency can be given by ${\nu }_0=\frac{v}{4(l+e)}$, where $v$ is the velocity of sound, $l$ is the length of the air column and $e=0.3\times \text{(diameter of the tube)}$ is the end correction.