An american system of communication is based on the radio frequency of 76 Hz. Compute the wavelength of theses waves and compare it to the diameter of the earth.

Answer 1

distance = speed * time

wavelength = speed * period
= speed / frequency

= 3 * 10^8 m/s / 76 = 3.95 * 10^6 meters
= 3950 km

Either you have a typo or you are talking about a super low frequency system that is used to communicate with submarines underwater.

It is 360 degrees around the equator each of 60 nautial miles
so
pi D = 60 * 360 = 21600 nautical miles circumference so
D = 6875 nautical miles = 12,733km
3950/12,733 = .31
radio wave is about 1/3 earth diameter