Question

When a metal plate is illuminated with a light of wavelength 310nm the emissions of photo electrons take place .if the stopping potential is 2volt the find the valve of work functio of metal plate
a) 1ev b ) 2ev c) 3ev d) 4ev

Answer 1

Answer : (b) 4λ

Explanation :

Einstein's photoelectric equation :

hcλ=e(3V0)+W−−−−(1)

Here W=work function ;     and hcλ=e(V0)+W−−−−(2)

Solving equations

(1)-(2)

hcλ=3hc2λ−W−3W

2W=hc2λ

hcλ0=hc4π

λ0=4λwhenλ0= threshold wavelength