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प्रश्न
Explain black body radiation spectrum in terms of wavelength
उत्तर
A perfectly black body emits radiation of all possible wavelength. The radiation emitted by black body depends upon its temperature. The graph between energy emitted and wavelength is called spectrum of black body radiation.
The graph between intensity of radiation Eλ vs λ for various temperature represents black body spectra. The spectra of black body radiation is as shown in the figure.
Observation:
a) Intensity of emitted radiation increases with increase of wavelength.
b) The intensity of emitted radiation is maximum for a particular wavelength (λmax) and
then intensity decreases with further increase in wavelength
c) Area under the curve (Eλ) versus (λ) represents total energy emitted per second per unit area by the black body including all the wavelength
Conclusion:
a) At a given temperature of black body:
- Energy distribution curve continues to be non-uniform.
- Energy emitted is maximum corresponding to specific wavelength (λmax) and falls on either side of it
- Total energy (E) emitted per second per unit area corresponding to all wavelengths is represented by the area under the curve
b) With the rise in temperature of black body:
- Total energy emitted increases rapidly for a given wavelength
- Peak of Eλ versus λ curve shifts towards left indicating decrease in value of λmax.
- The area enclosed by each curve with λ-axis increases.
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