When the energy of the incident radiation is increased by $20\%$, the kinetic energy of the photoelectrons…

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:
  1. $0.65 \, eV$
  2. $1.0 \, eV$
  3. $1.3 \, eV$
  4. $1.5 \, eV$

Solution

We know that, KEmax=hv- ψ

Let initial frequency of the light be ν and final frequency be ν'. According to question, final energy of light is 20% more than initial energy.

ν'=1.2ν

In the 1st case,
0.5 eV=hv- ψ   ...(i)

In the 2nd case,
0.8eV=1.2 hv- ψ   ...(ii)


Solving (i) and (ii) simultaneously, we get,

ψ  =1 eV

Asked in: NEET 2014

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