Question

The minimum energy needed to eject an electron from a sodium atom is 4.41 x 10-19 j. what is the maximum wavelength of light, in nanometers, that will show a photoelectric effect with sodium?

Answer 1

The energy of an electron as it is ejected from the atom can be calculated from the product of the Planck's constant and the frequency of the light energy. We can calculate the wavelength from the frequency we can calculate. We do as follows:

E = hv
 4.41 x 10-19  = 6.62607004 × 10-34 (v)
v = 6.66x10^14 /s

wavelength = speed of light / frequency

wavelength = 3x10^8 / 6.66x10^14
wavelength = 4.51x10^-7 m = 450.75 nm