Steafan-Boltzmann law, Planck's law, Wiens displacement law

Steafan-Boltzmann law

It states that the total energy emitted per unit area per unit time by a black body is directly proportional to the fourth power of its absolute temperature.

• The Steafan-Boltzmann equation is a fundamental relation for all the radiant energy transfer calculations.

E_b ∝  T⁴

E_b = σ  T⁴

• where

                T = temperature (K)

                σ = Steafan Boltzmann constant = 5.67 *10^-8  W/m².K⁴

E = e σ  T⁴..........................(E = e E_b)

                e = emissivity of the non-black body

Planck's law

This law gives a relationship between the monochromatic emissive power of a black body, absolute temperature, and the corresponding wavelength

• where

               Eb,λ = monochromatic emissive power of the black body, W/m2.μm

               h = Planck's constant

               k = Boltzmann constant

               c = speed of light

               T = absolute temperature

               λ = wavelength of radiation

• where C₁ and C₂ are constant

                  C₁ = 3.472*10^{^-16} W. m²and 

                  C₂ = 0.01439 m. K

Wiens displacement law

It states that the wavelength at which the maximum monochromatic emissive power is obtained (λ_max) is inversely proportional to the absolute temperature

Tλ_max = C

• where

                λ_max = wavelength (μm)

                T = temperature (K)

                C = 2890