Name: Standard Temperature and Pressure
Uploaded: 2019-07-19
Duration: 5 min 55 s
Description: What are the standard temperature and pressure values, as prescribed by IUPAC? Is it a constant, or can it be altered? Watch the video.

Question

Explain spectral distribution of blackbody radiation.

Accepted Answer

The spectral distribution of the thermal energy radiated by a blackbody depends only on its temperature.

The characteristics of blackbody radiation can be described in terms of several laws:

Planck’s Law of blackbody radiation, a formula to determine the spectral energy density of the emission at each wavelength ( $E_{λ}$ at a particular absolute temperature (T).

Wien’s Displacement Law, which states that the frequency of the peak of the emission ( $f_{\max}$ ) increases linearly with absolute temperature (T). Conversely, as the temperature of the body increases, the wavelength at the emission peak decreases. $f_{\max}$ ∝T

Stefan–Boltzmann Law, which relates the total energy emitted (E) to the absolute temperature (T).
E∝ $T^{4}$

In the image above, notice that:

The blackbody radiation curves have quite a complex shape (described by Planck’s Law).

The spectral profile (or curve) at a specific temperature corresponds to a specific peak wavelength, and vice versa.

As the temperature of the blackbody increases, the peak wavelength decreases (Wien’s Law).

The intensity (or flux ) at all wavelengths increases as the temperature of the blackbody increases.

The total energy being radiated (the area under the curve) increases rapidly as the temperature increases (Stefan–Boltzmann Law).

Although the intensity may be very low at very short or long wavelengths, at any temperature above absolute zero energy is theoretically emitted at all wavelengths (the blackbody radiation curves never reach zero).

Explain spectral distribution of blackbody radiation.

Important Questions on Kinetic Theory of Gases and Radiation

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