When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is [2014]

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Solution

Q.
When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is [2014]

1 0.65 eV

2 1.0 eV

3 1.3 eV

4 1.5 eV

Ans.
(2)

According to Einstein's photoelectric equation, the kinetic energy of emitted photoelectrons is

   $K = h υ - ϕ_{0}$

where $h υ$ is the energy of incident radiation and $ϕ_{0}$ is the work function of the metal.

As per question,

$0.5 eV = h υ - ϕ_{0}$ ...(i)

   $0.8 eV = 1.2 h υ - ϕ_{0}$ ...(ii)

On solving eqns. (i) and (ii), we get

   $ϕ_{0} = 1.0$ $eV$

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