RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    Star A has radius r, surface temperature T while star B has radius 4r and surface \[\frac{T}{2}\] temperature. The ratio of radiated power \[{{P}_{A}}\,:\,{{P}_{B}}\]from, then will be

    A)  1 : 4              

    B)  16 : 1

    C)  1 : 16             

    D)  1 : 1

    Correct Answer: D

    Solution :

     \[P=\sigma A{{t}^{4}}\] or           \[P\propto A{{T}^{4}}\] or            \[P\propto {{r}^{2}}{{T}^{4}}\]              \[(\because A=4\pi {{r}^{2}})\] \[\frac{{{P}_{A}}}{{{P}_{B}}}={{\left( \frac{{{r}_{A}}}{{{r}_{B}}} \right)}^{2}}{{\left( \frac{{{T}_{A}}}{{{T}_{B}}} \right)}^{4}}\] \[\frac{{{P}_{A}}}{{{P}_{B}}}={{\left( \frac{r}{4r} \right)}^{2}}{{\left( \frac{T}{T/2} \right)}^{4}}\] Or \[\frac{{{P}_{A}}}{{{P}_{B}}}=\frac{1}{{{(4)}^{2}}}\times {{(2)}^{4}}\] Or \[\frac{{{P}_{A}}}{{{P}_{B}}}=\frac{1}{16}\times 16\] \[\frac{{{P}_{A}}}{{{P}_{B}}}=\frac{1}{1}\]


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