NEET Sample Paper NEET Sample Test Paper-46

  • question_answer
    Assuming the Sun to have a spherical outer surface of radius r radiating like a black body at temperature\[t{}^\circ C\], the power received by a unit surface, (normal to the incident rays) at a distance R from the centre of the Sun is. (\[\sigma \]is Stefan constant) -

    A) \[\frac{4\pi {{r}^{2}}{{\sigma }^{4}}}{{{R}^{2}}}\]

    B)                    \[\frac{{{r}^{2}}\sigma {{(t+273)}^{4}}}{4\pi {{R}^{2}}}\]

    C)                    \[\frac{16{{\pi }^{2}}{{r}^{2}}\sigma t}{{{R}^{2}}}\]

    D)                    \[\frac{{{r}^{2}}\sigma {{(t+273)}^{4}}}{{{R}^{2}}}\]

    Correct Answer: D

    Solution :

    Power radiated by sun at \[t{}^\circ C\text{ }\,=\,\,\sigma {{\left( t\text{ }+\text{ }273 \right)}^{4}}4\pi {{r}^{2}}\] Power received by a unit surface area \[=\,\,\,\frac{\sigma {{(t+273)}^{4}}\,4\pi {{r}^{2}}}{4\pi {{R}^{2}}}\] \[=\,\,\,\frac{{{r}^{2}}\sigma {{(t+273)}^{4}}}{{{R}^{2}}}\]


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