In: Physics
White light (ranging in wavelengths from 380 to 750 nm) is incident on a metal with work function Wo = 2.68 eV.
1. For what range of wavelengths (from lmin to lmax) will NO electrons be emitted?
a) Imin=
b) Imax=
Einstein's Photoelectric equation, explain that a part of energy of photon ( hv) is used in liberating the electron from metal surface which is equal to work function (@0 ) .Rest part of energy of photon providing maximum kinetic energy ( 1/2*m*v2 ) to photon. It is given as:
hv = @0 + 1/2*m*v2max
hv ( frequency) = Energy of photon, @0 = work function. K.E = 1/2*m*v2
Electron emission will stop when bombarding photon has energy less than the work function.
So @0 = hv
v = @0 / h
v = 2.68*1.6*10-19 J / 6.63*10-34 J-s
v = 6.467*1014 hz
From , c = v*lambda ( by velocity ( c) = frequency (v) *wavelength (lambda) )
lambda = c / v
= 3*108 / 6.467*1014 = 463.8 nm
This refers to lmin = 463 nm where electron leaves with zero K.E
At any wavelength less than 463 nm no electron will be emitted.
Maximun wavelength = 750 nm is given in Q.
so No electron emission with lambda between 463 nm- 750 nm
lmin = 463 nm
lmax = 750nm