If $\phi$ is the work function of photosensitive material in eV and light of wavelength of numerical value…

If $\phi$ is the work function of photosensitive material in eV and light of wavelength of numerical value $\lambda=\frac{h c}{e}$ metre, is incident on it with energy above its threshold value at an instant then the maximum kinetic energy of the photo-electron ejected by it at that instant (Take $h$-Plank's constant, $c$-velocity of light in free space) is (in SI units):
  1. $e+2 \phi$
  2. $2 e-\phi$
  3. $e-\phi$
  4. $e+\phi$

Solution

$(\mathrm{K} . \mathrm{E})_{\max }=\frac{h c}{\lambda}-\phi_0$ and $\lambda=\frac{h c}{e}$ $\Rightarrow(\mathrm{K} . \mathrm{E})_{\max }=\frac{h c}{\frac{h c}{e}}-\phi_0$

Asked in: NEET 2024 (Re-NEET)

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