Radiation is the third mode of heat transfer. In this mode, the heat transmission takes place in form of waves. Radiation does not depend on medium for heat transfer. The best-known example of heat transfer from radiation is solar energy. It is recognized radiation which transfers heat in form of photons. The energy transmission by the radiating surface sun is not continuous, but it moves in form of packet. This packet is known as photons. These photons move in deep space and not change frequency over time.
Maxwell equation is not exact, as a theory of electromagnetism the Maxwell equation is successful to predicts various phenomenon. In between 1861 to 1862 Maxwell proposed electromagnet phenomenon of light which is published as Maxwell’s equations. According to Maxwell theory, the electromagnetic propagate in the form of the waves since the waves propagate through some medium. Then consider a hypothetical medium an Aether. Earlier it assumes Aether is filled in the whole universe.
Lambda = c/f
There are many types of electromagnetic waves (alpha, beta, gamma). These waves are categorized in wavelength and frequency. Thermal radiation includes visible and infrared light. In this period, firstly find the relative speed of Earth and Ether and the most celebrated experiment in this direction was performed. The visible portion of the spectrum is the range of frequency which can be visible in the human eye. X-rays are high energies.
2.Quantum theory or plank theory
Max Planck was German theoretical physicist. Plank won the Nobel Prize in Physics in 1918. Planks law explains electromagnetic radiation emission by any black body. Max plank develop and proposed a quantum theory in 1900. The concept of radiation emission in forms of photons or quanta. Each photon possesses a certain amount of energy which is directly proportional to its frequency of emission. the quantum of the electromagnetic field including electromagnetic radiation such as light, the EM waves are move in form of packet and this is known as photons.
h= plank’s constant
the photons have a certain amount of energy. The wavelength and frequency of EM radiation may vary, its speed in a vacuum remains constant at 3.0 x 108 m/sec, equal to the speed of light. When the electrons strike to the ground state, they emit energy of various wavelengths. And also, the prism is helping to develop some technology’s area.
The radiant energy emitted per unit area at per unit time from the surface of the black body. And the ratio of the emissive power of anybody to emissive power of the black body is known as emissivity.
It states that the emissivity of the surfaces is equal to its absorptivity when the surfaces or the body is in thermal equilibrium with respect to its surrounding. In other words, Kirchhoff’s law relates the thermal radiations to wavelength-specific radiative emission and absorption of the body. Gustav Kirchhoff published his law in several papers in 1859 and 1860.
4.Stephan Boltzmann Law
Stephan and Boltzmann are two different scientists. This law is accurate for black bodies (which absorb most of the radiation of different wavelengths). The prior law is based on experimental data, According to this law, the total emissive power of black bodies is directly proportional to the fourth power of its absolute temperature. With the help of Stephan Boltzmann’s law Stephan also determined the temperature on the surface of the sun. Mathematically,
Also read: heat flow – modes of heat transfer
Modern theories proposed that the thermal radiation does not require any medium for transport of energy because waves move continuously in every direction. Radiation is a totally different form of heat transfer and our greatest source of energy sun spread energy in the form of radiation. However, there is more scientist who proposed theories and laws about radiation but above noted are main of them. If you want to add one more or have some query please comment below.