J & K CET Medical J & K - CET Medical Solved Paper-2006

  • question_answer
    A black body at a temperature T radiates  energy at E. It the temperature falls to\[\frac{T}{2},\] the radiated energy will be :

    A)  \[\frac{E}{4}\]                                  

    B) \[\frac{E}{2}\]

    C)  \[2E\]                                                  

    D) \[\frac{E}{16}\]

    Correct Answer: D

    Solution :

                     From Stefan-Boltzmann's law the radiant energy E is proportional to fourth power of absolute temperature (T ) of a black body. \[E=\sigma {{T}^{4}}\]         (a = Stefan's constant) Given,   \[{{E}_{1}}=E,\,\,{{T}_{1}}=T,\,\,{{T}_{2}}=\frac{T}{2}\] \[\therefore \]  \[\frac{{{E}_{1}}}{{{E}_{2}}}=\frac{T_{1}^{4}}{T_{2}^{4}}\] \[\Rightarrow \]               \[{{E}_{2}}=\frac{T_{2}^{4}}{T_{1}^{4}}.{{E}_{1}}\] \[\Rightarrow \]               \[{{E}_{2}}=\frac{{{\left( \frac{T}{2} \right)}^{4}}}{{{T}^{4}}}.E=\frac{E}{16}\]


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