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

  • question_answer
    Two spheres of same material have radius 1m and 4 m and temperature 4000K and 2000K respectively. The energy radiated per second by the first sphere is      [Pb. PMT 2002]

    A)            Greater than that by the second

    B)            Less than that by the second

    C)            Equal in both cases

    D)            The information is incomplete

    Correct Answer: C

    Solution :

                       Energy radiated per sec \[\frac{Q}{t}=P=A\varepsilon \sigma {{T}^{4}}\] \[P\propto {{r}^{2}}{{T}^{4}}\Rightarrow \frac{{{P}_{2}}}{{{P}_{1}}}=\frac{r_{2}^{2}}{r_{1}^{2}}.\frac{T_{2}^{4}}{T_{1}^{4}}=\frac{{{4}^{2}}}{{{1}^{2}}}\times {{\left( \frac{2000}{4000} \right)}^{4}}=1\]


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