Question

Ultraviolet light of wave-length 2271 Å from a 100 W mercury source radiates a photocell made of molybednum metal. If the stopping potential is 1.3 V, estimate the work function of the metal. How would the photocell respond to high intensity (10⁸ W m^-2) red light of wavelength 6328 Å produced by a He-Ne laser?

Plot a graph showing the variation of photoelectric current with anode potential for two light beams of the same wavelength but different intensity.

Answer 1

Stopping potental of molybednum = 1.3 V

∴ Work function of molybednum = 1.3 eV

Energy of photon of red light,

As E is more than the work function of molybednum, hence it will emit electrons.

Since wavelength of two sources is the same but intensity is different, so stopping potential is the same and saturation current will be more for more intense light as shown in Fig.