NEET NEET SOLVED PAPER 2015 (C)

  • question_answer
    A radiation of energy E falls normally on a perfectly reflecting surface. The momentum on a transferred to the surface is (c = velocity of light)                                                                                                  

    A)  \[\frac{E}{c}\]                  

    B)  \[\frac{2E}{c}\]                

    C)  \[\frac{2E}{{{c}^{2}}}\]                 

    D)  \[\frac{E}{{{c}^{2}}}\]

    Correct Answer: B

    Solution :

    The radiation energy is given by \[E=\frac{hc}{\lambda }\] Initial momentum of the radiation is \[{{\mathbf{P}}_{i}}=\frac{h}{\lambda }=\frac{E}{c}\] The reflected momentum is \[{{\mathbf{P}}_{r}}=-\frac{h}{\lambda }=-\frac{E}{c}\] So, the change in momentum of light is \[\Delta {{\mathbf{P}}_{light}}={{\mathbf{P}}_{r}}-{{\mathbf{P}}_{i}}=-\frac{2E}{c}\] Thus, the momentum transferred to the surface is \[\Delta {{\mathbf{P}}_{light}}=\frac{2E}{c}\]


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