JEE Main · 2021 · 26 Feb 2021 · Shift 2 · Waves & Sound

WhatsApp Email

A tuning fork A of unknown frequency produces 5 beats/s with a fork of known frequency 340 Hz. When fork A is filed, the beat frequency decreases to 2 beats/s. What is the frequency of fork A?

(A)345 Hz
(B)338 Hz
(C)342 Hz
(D)335 Hz✓ Correct

Answer: (D)

Solution

Five beats per second against a

340

Hz fork puts the unknown frequency at either

345

Hz or

335

Hz. Filing a fork takes material off the prongs, which stiffens them relative to their mass and raises the frequency. Had the fork been at

345

Hz, filing would move it further above

340

Hz and the beat frequency would grow; the beat frequency instead drops to two per second, so filing moved the fork towards

340

Hz from below. The frequency of the fork is

335

Hz.

JEE Main · 2021 · 26 Feb 2021 · Shift 2 · Single correct option

Practise more: all JEE Main PYQs on Waves & Sound →

More JEE Main questions on Waves & Sound

Two loudspeakers ( $L_{1}$ and $L_{2}$ ) are placed with a separation of 10 m , as shown in figure. Both speakers are fed with an audio input signal of same frequency with constant volume. A voice recorder, initially at point $A$ , at equidistance to both loud speakers, is m …
JEE Main 2026View solution →
In an open organ pipe $v_{3}$ and $v_{6}$ are $3^{rd}$ and $6^{th}$ harmonic frequencies, respectively. If $v_{6} - v_{3} = 2200$ Hz then length of the pipe is $____$ mm. (Take velocity of sound in air is $330$ m/s.)
JEE Main 2026View solution →
The velocity of sound in air is doubled when the temperature is raised from $0^{\circ} C$ to $α^{\circ} C$ . The value of $α$ is ______.
JEE Main 2026View solution →
The fifth harmonic of a closed organ pipe is found to be in unison with the first harmonic of an open pipe. The ratio of lengths of closed pipe to that of the open pipe is 5/x. The value of x is ____.
JEE Main 2026View solution →
A point source is kept at the center of a spherically enclosed detector. If the volume of the detector increased by 8 times, the intensity will
JEE Main 2026View solution →
The speed of a longitudinal wave in a metallic bar is $400 m / s$ . If the density and Young's modulus of the bar material are increased by $0.5%$ and $1%$ respectively then the speed of the wave is changed approximately to ______ …
JEE Main 2026View solution →