JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Mock Test - Modern Physics

  • question_answer
    The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is 1 4 kilowatt/\[{{m}^{2}}\]. The average earth- sun distance is \[1.5\times {{10}^{11}}\] meters. The mass lost by the sun per day is (1 day = 86400 seconds)

    A) \[4.4\times {{10}^{9}}\,kg\]     

    B) \[7.6\times {{10}^{14}}\,kg\]

    C) \[3.8\times {{10}^{12}}\,kg\]    

    D) \[3.8\times {{10}^{14}}\,kg\]  

    Correct Answer: D

    Solution :

    [d] energy radiated \[=1.4KW/{{m}^{2}}\] \[=1.4KJ/\sec {{m}^{2}}=\frac{1.4kJ}{\frac{1}{86400}day\,{{m}^{2}}}=\frac{1.4\times 86400}{day\,{{m}^{2}}}\] Total energy radiated/day \[=\frac{4\pi \,{{(1.5\times {{10}^{11}})}^{2}}\times 1.4\times 86400}{I}\frac{kJ}{day}=E\] \[\therefore \]      \[E=m{{c}^{2}}\Rightarrow m=\frac{E}{{{c}^{2}}}\] \[=\frac{4\pi {{(1.5\times {{10}^{11}})}^{2}}\times 1.4\times 86400}{{{(3\times {{10}^{8}})}^{2}}}=3.8\times {{10}^{14}}kg.\]


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