JEE PYQ: Waves And Sound Question 8
Question 8 - 2021 (26 Feb Shift 2)
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?
(1) 342 Hz
(2) 335 Hz
(3) 338 Hz
(4) 345 Hz
Show Answer
Answer: (2)
Solution
Before filing: answer should be 335 Hz or 345 Hz.
After filing: frequency increases. If original frequency was 335 Hz, filing increases it to 336, 337, 338… Beat frequency decreases from 5 to 2.
If original frequency was 345 Hz, filing increases it to 346, 347, 348… Beat frequency increases.
After filed, beat/sec decreases only in case of 335 Hz.
BETA
