In an experiment tungsten cathode which has a threshold `2300 Å` is irradiated by ultraviolet light of wavelength `1800Å`. Calculate
(i) Maximum energy of emitted photoelectron and
(ii) Work function for tungsten.
(Mention both the results in electron-volts)
Given Planck's constant `h=6.6 xx 10^(-34) joule-sec`, `leV = 1.6 xx 10^(-19)` joule and velocity of light `c= 3xx10^(8)m//sec`

Explanation

The work function of tungsten cathode is
`phi= (hc)/(lambda_(th))= (12431)/(2300)eV` = eV
The energy in eV of incident photons is
`E=(hc)/(lambda) = (12431)/(1800)eV`
The maximum kinetic energy of ejected electrons can be given as
`KE_("max") = E-phi = 6.9-5.4eV = 1.5eV`