Question

Two cars $A$ and $B$ approach a stationary observer from opposite sides as shown in fig. Observer hears no beats. If the frequency of the horn of the car $B$ is $504Hz$, the frequency of horn of car $A$ will be :

• A. $529.2Hz$
• B. $295.2Hz$
• C. $440.5Hz$
• D. none of these

Answer 1

Answer: (A)

$529.2Hz$

Since, the person hears no beats therefore their apparent frequency are the same.
So, $n\times \frac{330}{330-15}=504\times \frac{330}{330-30}$
$n=\frac{504\times 315}{300}=529.2Hz$