Wave property of electrons implies that they will show diffraction effects. Davission and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure)

The surface of a metal is illuminated with the light of `400 nm`. The kinetic energy of the ejected photoelectrons was found to be `1.68 eV`. The work function of the metal is : (`hc = 1240 eV-nm`)

Options

A. `1.51 eV`
B. `1.68 eV`
C. `3.09 eV`
D. `1.42 eV`

Answer

D

Explanation

`E_(k)=(hc)/lambda- phi_(0) implies 1.68 =12400/4000- phi_(0)`
By solving it `" "phi_(0)=1.42 eV`