Question

If a sound wave has frequency of 30 Hz, then it will vibrate _____ times in $\frac{1}{2}$ minute.

• A. 1800
• B. 15
• C. 900
• D. 60

Answer 1

The correct option is C 900

Frequency of sound wave, f = 30 Hz = 30 vibrations/second

$\therefore$ Number of vibrations in 1 s = 30

Time, $t=\frac{1}{2}minute=30s$

Number of vibrations in $30s,n=f\times t=30\times 30=900$

Hence, the correct answer is option (c).