Question

A source emits a sound of frequency of $400Hz$ , but the listener hears its to be $390Hz$ . Then

• A. the listener is moving towards the source
• B. the source is moving towards the listener
• C. the listener is moving away from the source
• D. the listener has a defective ear

Answer 1

Answer: (C)

Real frequency, $n=400Hz$
Apparent frequency , $n^{\prime }=390Hz$
$n^{\prime }<n$
So, the distance between the source and listener increases or the listener is moving away from source