CMC Medical CMC-Medical VELLORE Solved Paper-2008

  • question_answer
    A black body emits radiations of maximum intensity for the wavelength of 5000\[\overset{\text{o}}{\mathop{\text{A}}}\,\] when the temperature of the body is \[1227\,{}^\circ C\]. If the temperature of the body is increased by \[1000{}^\circ C,\] the maximum intensity would be observed at

    A)  1000 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]                          

    B)  2000 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C)  5000 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]          

    D)  4000 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]

    E)  3000 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: E

    Solution :

                    According to Wiens displacement law, if maximum energy is emitted at wavelength \[{{\lambda }_{m}}\] at temperature T, then \[{{\lambda }_{m}}\] T = constant or            \[{{\lambda }_{m}}\propto \frac{1}{T}\] or            \[\frac{{{({{\lambda }_{m}})}_{1}}}{{{({{\lambda }_{m}})}_{2}}}=\frac{{{T}_{2}}}{{{T}_{1}}}\] \[\therefore \]  \[\frac{5000}{{{({{\lambda }_{m}})}_{2}}}=\frac{2227+273}{1227+273}\] or            \[\frac{5000}{{{({{\lambda }_{m}})}_{2}}}=\frac{2500}{1500}\] \[\therefore \]  \[{{({{\lambda }_{m}})}_{2}}=3000\overset{\text{o}}{\mathop{\text{A}}}\,\]


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