Question

A dog can hear sounds in the range from 15 to 50,000 hz. what wavelength corresponds to the lower cut-off point of the sounds at 20◦c? answer in units of m.

Answer 1

The frequency corresponding to the lower cut-off point is 
$f=15 Hz$
The speed of sound at a temperature of $20^{\circ}C$ is approximately
$v=343 m/s$

Therefore we can use the relationship between speed of a wave, frequency and wavelength to calculate the corresponding wavelength:
$\lambda= \frac{v}{f}= \frac{343 m/s}{15 Hz}=22.87 m$
So, the corresponding wavelength is 22.87 m.