Answer:
a)
b)
Explanation:
For this case we have the following frequency given:
We can convert this into Hz like this:
If we have a fundamental wave we need to satisfy the following condition:
If we solve for the wavelength we got:
We know that the velocity of the light is
And if we replace into the last formula we got:
Part b
For this case we can use the same formula but on this case the velocity of the sound at 20C is approximately 343 m/s, the frequency is given by:
We use the same wavelenght from the previous part
And if we replace the new values we got: