J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    Solar radiation emitted by sun correspond to that emitted by black body at a temperature of \[6000\text{ }K\]. Maximum intensity is emitted at wavelength of\[4800\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]. If the sun was to cool down from \[6000\text{ }K\]to \[3000\text{ }K,\] then the peak intensity of emitted radiation would occur at a wavelength

    A)  \[4800\overset{\text{o}}{\mathop{\text{A}}}\,\]      

    B)  \[9600\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C)  \[2400\overset{\text{o}}{\mathop{\text{A}}}\,\]      

    D)  \[19200\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: B

    Solution :

    Wein's displacement law states that there is an inverse relationship between the wavelength \[({{\lambda }_{m}})\] of the peak of the emission of a black body and its temperature (T). \[\therefore \] \[{{\lambda }_{m}}=\frac{b}{T}\] (b = constant) \[\therefore \] \[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{{{T}_{2}}}{{{T}_{1}}}\] \[\Rightarrow \] \[{{\lambda }_{2}}=\frac{{{\lambda }_{1}}{{T}_{1}}}{{{T}_{2}}}\] Given,  \[{{\lambda }_{1}}=4800\overset{\text{o}}{\mathop{\text{A}}}\,,\,\,\,\,{{T}_{1}}=6000K,\] \[{{T}_{2}}=3000K,\] \[\therefore \] \[{{\lambda }_{2}}=\frac{4800\times 6000}{3000}=9600\overset{\text{o}}{\mathop{\text{A}}}\,\]


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