Question

A source of sound gives five beats per second, when sounded with another source of frequency $100s^{-1}$. The second harmonic of the source together with a source of frequency $205s^{-1}$ gives $5\text{beats}/\text{sec}$. The frequency of the first source is

• A. $105s^{-1}$
• B. $205s^{-1}$
• C. $95s^{-1}$
• D. $100s^{-1}$

Answer 1

The correct option is A $105s^{-1}$

Frequency of source can be $95Hz$ or $105Hz$ whose corresponding second harmonics will be $190Hz$ or $210Hz$ out of which only $210Hz$ can give $5\text{beats}/\text{sec}$ with $205Hz$ source. Hence, frequency of source is $105Hz$.

option (a)