JEE Main & Advanced Physics Transmission of Heat Question Bank Radiation Stefan's law

  • question_answer
    The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is                                         [EAMCET 2003]

    A)            300 : 1                                     

    B)            600 : 1

    C)            900 : 1                                     

    D)            1200 : 1

    Correct Answer: C

    Solution :

                       \[Q\propto A{{T}^{4}}\propto {{r}^{2}}{{T}^{4}}\]\[\Rightarrow \frac{{{Q}_{\text{star}}}}{{{Q}_{\text{sun}}}}=\frac{{{r}^{2}}_{\text{star}}.{{T}^{4}}_{\text{star}}}{{{r}^{2}}_{\text{sun}}\times T_{sun}^{4}}\]            \[\Rightarrow \frac{10000}{1}=\frac{r_{\text{star}}^{2}}{r_{\text{sun}}^{2}}\times {{\left( \frac{6000}{2000} \right)}^{4}}\]\[\Rightarrow \frac{{{r}_{\text{star}}}}{{{r}_{\text{sun}}}}=\frac{100\times 9}{1}=\frac{900}{1}\]


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