JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Critical Thinking

  • question_answer
    A photon of wavelength 6630 Å is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

    A)            6.63 ´ 10?27 kg-m/sec       

    B)            2 ´ 10?27 kg-m/sec

    C)            10?27 kg-m/sec                    

    D)            None of these

    Correct Answer: B

    Solution :

                       The momentum of the incident radiation is given as \[p=\frac{h}{\lambda }\]. When the light is totally reflected normal to the surface the direction of the ray is reversed. That means it reverses the direction of it?s momentum without changing it?s magnitude \ \[\Delta p=2p=\frac{2h}{\lambda }=\frac{2\times 6.6\times {{10}^{-34}}}{6630\times {{10}^{-10}}}\]= 2 ´ 10?27 kg-m/sec.


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