Question

An unknown tuning fork when sounded together with a tuning fork of frequency $\text{256 Hz}$ emits two beats. On loading the tuning fork of frequency $\text{256 Hz}$ , the number of beats heard is $1$ per second. The frequency (in $Hz$ ) of the unknown tuning fork is

• A. $\text{257}$
• B. $\text{258}$
• C. $\text{256}$
• D. $\text{254}$

Answer 1

Answer: (D)

$n_A=$ Known frequency $=256Hz$ , $n_B=?$
$x=2bps$ , which is decreasing after loading $\left(i.e.x\downarrow \right)$
Known tuning fork is loaded so $n_A\downarrow$
Hence $n_A\downarrow -n_B=x\downarrow$ .....(i) Correct
$n_B-n_A\downarrow =x\downarrow$ .....(ii) Wrong
$\Rightarrow$ $n_B=n_A-x=256-2=254Hz$