The relationship between the speed, the frequency and the wavelength of a wave is given by:

where
f is the frequency
v is the speed of the wave

is its wavelength
for the pressure wave in this problem,

and v=1400 m/s, therefore its frequency is
Answer: i think he's done 50% of work
Explanation:
The filter would need to absorb every color EXCEPT yellow. It would have to absorb red orange green blue and violet.