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NEET Sample Paper NEET Sample Test Paper-77

  • question_answer
    If a monochromatic light of frequency \[6.0 \times  1{{0}^{14}}Hz\] is produced by a source and the power emitted is \[2.0 \times  1{{0}^{-}}^{3}W\], then the number of photons emitted per second by the source is

    A)  \[3\,\,\times \,\,1{{0}^{10}}\]              

    B)  \[5\,\,\times \,\,1{{0}^{15}}\]

    C)  \[7\,\,\times \,\,1{{0}^{12}}\]              

    D)  \[9\,\,\times \,\,1{{0}^{12}}\]

    Correct Answer: B

    Solution :

    As energy, \[\operatorname{E}=h\nu =6.63\times 1{{0}^{-\,34}}\,\times 6.0 \times 1{{0}^{14}}\] \[=\,\,3.98\times 1{{0}^{-}}^{19}\,J\] Now, number of photons emitted per second \[n=\frac{p}{E}\] \[=\,\,\,\frac{2.0\times {{10}^{-\,3}}\,W}{3.98\times {{10}^{-\,19}}\,J}\] \[= \,\,5 \times 1{{0}^{15}}\] photons per second


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