JEE MAIN - Physics (2021 - 26th February Evening Shift - No. 18)
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?
335 Hz
345 Hz
338 Hz
342 Hz
Explanation
Initially beat frequency = 5Hz
so, $$\rho$$A = 340 $$ \pm $$ 5 = 345 Hz, or 335 Hz
after filing frequency increases slightly so, new value of frequency of A > $$\rho$$A
Now, beat frequency = 2Hz
$$ \Rightarrow $$ new $$\rho$$A = 340 $$ \pm $$ 2 = 342 Hz, or 338 Hz
hence, original frequency of A is $$\rho$$A = 335 Hz
so, $$\rho$$A = 340 $$ \pm $$ 5 = 345 Hz, or 335 Hz
after filing frequency increases slightly so, new value of frequency of A > $$\rho$$A
Now, beat frequency = 2Hz
$$ \Rightarrow $$ new $$\rho$$A = 340 $$ \pm $$ 2 = 342 Hz, or 338 Hz
hence, original frequency of A is $$\rho$$A = 335 Hz
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