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CMC Medical CMC-Medical Ludhiana Solved Paper-2008

  • question_answer
    A photosensitive surface is receiving light of wavelength 5000\[\overset{\text{o}}{\mathop{\text{A}}}\,\] at the rate of\[{{10}^{-7}}\,J\text{/}s.\]. The number of photons ejected per second is

    A)  \[2.5\times {{10}^{12}}\]                            

    B)  \[2.5\times {{10}^{11}}\]

    C)  \[2.5\times {{10}^{10}}\]                            

    D)  \[2.5\times {{10}^{9}}\]

    Correct Answer: B

    Solution :

                    According to Plancks quantisation law, \[E=nhv=n\left( \frac{hc}{\lambda } \right)\] \[\Rightarrow \]               \[\frac{E}{t}=\left( \frac{n}{t} \right)\left( \frac{hc}{\lambda } \right)\] \[\Rightarrow \]               \[{{10}^{-7}}=\left( \frac{n}{t} \right)\frac{6.626\times {{10}^{-34}}\times 3\times {{10}^{8}}}{5000\times {{10}^{-10}}}\] \[\Rightarrow \]               \[\frac{n}{t}=\frac{5000\times {{10}^{-10}}\times {{10}^{7}}}{6.626\times {{10}^{-34}}\times 3\times {{10}^{8}}}\] \[\Rightarrow \]               \[\frac{n}{t}=2.5\times {{10}^{11}}s\]


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