4. What is the frequency of an electromagnetic wave with a wavelength
of 20 m?

The frequency of radio waves with a wavelength of 20m is

1.5 e+7 Hertz (Hz) or 15 million Hertz.

This was obtained from the formula speed (c) is equal to the product of frequency (f) and wavelength (λ)

c = fλ  

Since we are looking for the frequency, we will divide both sides of the formula above by the lamda symbol for wavelength, which gives us:

f = c / λ

The value of wavelength is already given which is 20 meters. The speed of radio waves is the same with the speed of light when travelling in a vacuum – also with the other electromagnetic waves. Hence the speed (c) is 3 e+8 m/s

f = 3 e+8 m/s   /    20m

f = 1.5 e+7 H

Explanation:

this is the correct answer you want.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees.