Question

Find out the change in wavelength of a $700Hz$ acoustic wave as it enters brass from warm air? Given Speed of Sound in warm air is $350m/s$ and through brass is $3,500m/s$.

• A. It decreases by a factor of $20$
• B. It decreases by a factor of $10$
• C. It increases by a factor of $10$
• D. It increases by a factor of $20$
• E. The wavelength remains unchanged when a wave passes into a new medium

Answer 1

Answer: (C)

It increases by a factor of $10$

Given : $\nu =700$ $Hz$ $v_a=350m/s$ $v_b=3500m/s$

Using $v=\nu \lambda$

$\therefore$ ${\lambda }_a=\frac{v_a}{\nu }=\frac{350}{700}=0.5$ $m$

Similarly ${\lambda }_b=\frac{v_b}{\nu }=\frac{3500}{700}=5$ $m$

Thus wavelength increases by a factor of $10$