In a photoelectric experiment, ultraviolet light of wavelength 280   nm is used with lithium cathode…

In a photoelectric experiment, ultraviolet light of wavelength 280 nm is used with lithium cathode having work function ϕ=2.5 eV. If the wavelength of incident light is switched to 400 nm, find out the change in the stopping potential.

h=6.63×10-34 J s, c=3×108 m s-1

  1. 1.1 V
  2. 0.6 V
  3. 1.3 V
  4. 1.9 V

Solution

From the photoelectric equation,

eV0=hcλ−ϕ

Using this equation for the given two cases,

eV1=hc280 nm−ϕ

eV2=hc400 nm−ϕ

On subtracting,

eV1−V2=1240120280×400                   =1.3 eV

⇒V1−V2=1.3 V

Asked in: JEE Main 2021 (26 Aug Shift 1)

Practice more Dual Nature of Matter and Radiation questions on Aicharya