IIT-JEE 2009 · Paper 2 · Physics Q44

← IIT-JEE 2009 · Paper 2

PhysicsMultiple correct+4 / -1Question 44 of 57

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,

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

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

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

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 and worked solution

Official answer: A, D

(A) The sound spreads out and is damped more over the longer column, so the first resonance is louder. True.
(B) The prongs are held in a vertical plane so that they vibrate along the tube's axis. False.
(C) The prongs vibrate with amplitudes of a fraction of a millimetre, not 1 cm. False.
(D) Because of the end correction $e$ , $l_1=\frac\lambda4-e$ , a little shorter than $\frac\lambda4$ . True.

(A), (D)

Topics:Speed of sound by resonance tube Organ pipes and resonance

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IIT-JEE 2009 · Paper 2, Physics question 44