If it takes 6.6E-7 seconds for one wavelength of a wave to pass a stationary point, what is the frequency of the wave in Hz?
I cannot figure out what equation to use or how to use it.
You have to assume this is light, traveling at the speed of light.
wavelength= speedlight*6.6E-7=200m
frequency= 3E8m/s / 200m= you finish it.