We need to estimate the period of oscillation of an electron that bounced up/down due to the effects of a passing packet of red light. The period of oscillation is the wavelength of the red light divided by the speed of the red light. We know that:
V = f*λ
where V = speed of the red light = 3*10^8 m/s
f = frequency = 1/T where T is the period of oscillation in seconds (s)
