Question

A source produces sound waves under water. Waves travel through water and then into air. Which of the following statements about the frequency ($f$) and the wavelength ($\lambda$) is correct as sound passes from water to air?

• A. $f$ remains unchanged but $\lambda$ decreases
• B. $f$ remains unchanged but $\lambda$ increases
• C. $\lambda$ unchanged but $f$ decreases
• D. $\lambda$ unchanged but $f$ increases

Answer 1

Answer: (A)

$f$ remains unchanged but $\lambda$ decreases

Since sound is travelling from water to aid
Therefore frequency remains constant it depends on the source of sound
Now $v=f\lambda$
If $v$ will decrease then $\lambda$ will also decrease as $f$ is constant.