NEET NEET SOLVED PAPER 2014

  • question_answer
    Light with an energy flux of \[25\times {{10}^{4}}W{{m}^{-2}}\] falls on a perfectly reflecting surface at normal incidence. If the surface area is 15\[c{{m}^{2}}\], the average force exerted on the surface is [AIPMT 2014]

    A)  \[1.25\times {{10}^{-6}}N\]      

    B)  \[2.50\times {{10}^{-6}}N\]

    C)  \[1.20\times {{10}^{-6}}N\]     

    D)  \[3.0\times {{10}^{-6}}N\]

    Correct Answer: A

    Solution :

    Energy flux = \[\frac{25\times {{10}^{4}}\text{J}}{s{{m}^{2}}}\] Force on unit area = momentum transferred in unit time on unit area \[=\frac{25\times {{10}^{4}}}{C}\] \[=\frac{25\times {{10}^{4}}}{3\times {{10}^{8}}}\] \[=\,8.3\times {{10}^{-4}}N/{{m}^{2}}\] Force on the \[15\times {{10}^{-4}}{{m}^{2}}\] area \[=8.3\times {{10}^{-4}}N/{{m}^{2}}\times 15\times {{10}^{-4}}{{m}^{2}}\] \[=124.5\times {{10}^{-8}}N\] \[1.25\times {{10}^{-6}}N\]


You need to login to perform this action.
You will be redirected in 3 sec spinner