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The work function of a metal is 4.2 eV. ...

The work function of a metal is `4.2 eV`. If radiation of `2000 Ã` fall on the metal then the kinetic energy of the fastest photoelectron is

A

`1.6 xx 10^(-19)J`

B

`16 xx 10^(10) J`

C

`3.2 xx 10^(-19) J`

D

`6.4 xx 10^(-10)J`

Text Solution

Verified by Experts

The correct Answer is:
C
K.E. of photoelectron = (Energy of radiation - Work function)
`= [(hc)/(lambda)-4.2 eV]`
`[(6.6 xx 10^(-34) xx 3 xx 10^(8))/(2000 xx 10^(-10))-4.2 xx 1.602 xx 10^(-19)]`
`= 9.9 xx 10^(-19)J - 6.7 xx 10^(-19) J = 3.2 xx 10^(-19)J`
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