Answer
The highest frequency heard by a student is 619 Hz and the lowest frequency is 582 Hz
Work Step by Step
We can find the speed of the sound generator as:
$v = (100~rpm)\times \frac{(2\pi)(1.0~m)}{1~rev}\times (\frac{1~min}{60~s})$
$v = 10.5~m/s$
We can find the highest frequency heard by a stationary observer.
$f' = \frac{f}{(1-\frac{v_{source}}{v_{snd}})}$
$f' = \frac{600~Hz}{(1-\frac{10.5~m/s}{343~m/s}~)}$
$f' = 619~Hz$
We can find the lowest frequency heard by a stationary observer.
$f' = \frac{f}{(1+\frac{v_{source}}{v_{snd}})}$
$f' = \frac{600~Hz}{(1+\frac{10.5~m/s}{343~m/s}~)}$
$f' = 582~Hz$
The highest frequency heard by a student is 619 Hz and the lowest frequency is 582 Hz.
