Using a radar gun, you emit radar waves at a frequency of 2.6 GHz that bounce off of a moving tennis ball and recombine with the original waves. This produces a beat frequency of 730 Hz. How fast was the tennis ball moving?
fbeat = fa - fb
The Attempt at a Solution
I found the frequency that bounces back from the moving tennis ball using fbeat=fa-fb, however, I don't know how to find that speed of the tennis ball given that I don't know its wavelength.