CalcuLate the velocity of an electron ejected if 300.0 mm of light is applied to the surface. A wavelength of 795 nm has sufficient energy to eject electrons.

The equation relating velocity and wavelength is written below:

v = λf

where λ is the wavelength in m while f is frequency in 1/s.

Let's determine first the frequency from the speed of light:

c = distance/time, where c is the speed of light equal to 3*10⁸ m/s

3*10⁸ m/s = (300 mm) (1 m/1000 mm) / time

time = 1*10⁻⁹ seconds

Since f = 1/t,

f = 1/1*10⁻⁹ seconds = 10⁹ s⁻¹

Thus,

v = (795*10⁻⁹ m) (10⁹ s⁻¹)

v = 795 m/s