JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Photon and Photoelectric Effect

  • question_answer
    If we express the energy of a photon in KeV and the wavelength in angstroms, then energy of a photon can be calculated from the relation                           [AMU (Engg.) 1999]

    A)            \[E=12.4\,h\nu \]               

    B)            \[E=12.4\,h/\lambda \]

    C)            \[E=12.4\,/\lambda \]      

    D)            \[E=h\nu \]

    Correct Answer: C

    Solution :

                       Energy of photon \[E=\frac{hc}{\lambda }\] (Joules) \[=\frac{hc}{e\lambda }(eV)\]                    \[\Rightarrow \,\underset{(eV)}{\mathop{E}}\,=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{1.6\times {{10}^{-19}}\times \lambda ({\AA})}=\frac{12375}{\lambda ({\AA})}\]            \[\Rightarrow \,\,E(keV)=\frac{12.37}{\lambda ({\AA})}\approx \frac{12.4}{\lambda }\]


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