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 five beats per second. What is the frequency of the source

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

Answer 1

Answer: (A)

$105s^{- 1}$

Answer 2

Frequency of the source = 100 ± 5 = 105 Hz or 95 Hz.

Second harmonic of the source = 210 Hz or 190 Hz.

As the second harmonic gives 5 beats/sec with sound of frequency 205 Hz, the second harmonic should be 210 Hz.

⇒ Frequency of the source = 105 Hz.