posted by sh .
The wavelength of red light is about 7x10^-7m. The frequency of the red light reflected from a metal surface and the frequency of the vibrating electron that products it are the same. What is this frequency?
It goes 7x10^-7m at 3*10^8 m/s in one period so the period = 7*10^-7/3*10^8 and the frequency is one over the period.