Spectral Energy Density, Total Energy Density, Emmisive Power & Absorptive Power

Spectral Energy Density: 

Spectral Energy Density for a particular wave length is the energy per unit volume per unit range of wavelength.


Total Energy Density:


Total Energy Density of Thermal Radiation at any point is the total radiant energy per unit volume around that point due to all wavelengths.

Emmisive Power:

The emmisive power of a body at a given temperature and for a given wavelength, is defined as the ratio of the radiant energy absorbed for second by unit surface area of the body per unit wavelength range.


Absorptive Power


The absorptive power of a body at a given temperature and wavelength is defined as the ratio of radiant energy absorbed per second by unit surface area of the body to the total energy falling per second on the same area.   

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