Light of wavelength 4000 mathringA is incident on a metal plate whose work function is 2 eV. The maximum kinetic energy of the emitted photo-electron will be :

Question

Light of wavelength 4000 mathringA is incident on a metal plate whose work function is 2 eV. The maximum kinetic energy of the emitted photo-electron will be : (A) 0.5 eV (B) 1.1 eV (C) 1.5 eV (D) 2.0 eV

Tardigrade Admin · Accepted Answer

When maximum kinetic energy of photoelectrons is

E_{K}

, and

W

is work function of metal, then from Einstein's photoelectric equation.

E_{K} = h v - W

where

h v

is energy of photon absorbed in the metal.
Also

E = h v = \frac{h c}{λ}

E = \frac{6.6 \times 1 0 ^{- 34} \times 3 \times 1 0 ^{8}}{4000 \times 1 0 ^{- 10} \times 1.6 \times 1 0 ^{- 19}} e V

= 0.31 e V

∴ E_{k} = 3.1 - 2

= 1.1 e V

Note : Photoelectrons are emitted when energy of incident photon is more than work function of the metal

Q. Light of wavelength 4000A˚ is incident on a metal plate whose work function is 2eV. The maximum kinetic energy of the emitted photo-electron will be :

0.5 eV

1.1 eV

1.5 eV

2.0 eV

Q. Light of wavelength $4000 \overset{˚}{A}$ is incident on a metal plate whose work function is $2 e V$ . The maximum kinetic energy of the emitted photo-electron will be :