A) \[x=2h\]
B) \[x=h\]
C) \[{{10}^{7}}\,\,\pi J\]
D) \[{{10}^{4}}\,\,\pi J\]
Correct Answer: B
Solution :
When maximum kinetic energy of photoelectrons is \[{{E}_{K}},\] and \[W\] is work function of metal, then from Einstein?s photoelectric equation. \[{{E}_{K}}=hv-W\] Where \[hv\] is energy of photon absorbed in the metal. Also \[E=hv=\frac{hc}{\lambda },\] \[E=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{4000\times {{10}^{-10}}\times 1.6\times {{10}^{-19}}}ev\] \[=0.31\,\,eV\] \[\therefore \] \[{{E}_{k}}=3.1-2=1.1\,\,eV\] Note: Photoelectrons are emitted when energy of incident photon is more than work function of the metal.
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