A photon of wavelength 3310 falling on a photo cathode ejects an electron of energy 3 × 10–19 J and one of wavelength 5000 ejects an electron of energy 0.972 × 10–19 J. Calculate the value of Planck’* constant and the threshold wavelength for the photo cathode.
In the first case,
In the second case,
Subtracting one from the other,
h = 6.62 × 10–34 J-*
Substituting this value of h, W0 = 3 × 10–19 J
