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JEE Main & Advanced Sample Paper JEE Main Sample Paper-40

  • question_answer
    At a specific temperature, the energy densities for a black body for three different wavelengths are 10, 19 and 7 units. For these wavelengths if the absorption coefficient of a body is respectively 0.8, 0.3 and 0.9 then the emissive powers of this body for these wavelengths are in the ratio             

    A) 10:19:7                       

    B) 8:3:9                    

    C) 8:5.7:6.3                     

    D) 8:9.5:4.3

    Correct Answer: C

    Solution :

    Emissive power \[=a\in \] \[{{a}_{1}}{{\in }_{1}}:{{a}_{2}}{{\in }_{2}}:{{a}_{3}}{{\in }_{3}}\] \[\Rightarrow \]\[10\times \frac{8}{10}:\frac{3}{10}\times 19:7\times \frac{9}{10}\] \[\Rightarrow \]8:5.7:6.3


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