Difference Between Radiation and Irradiation

Radiation vs Irradiation

Radiation and irradiation are two processes discussed in physics and other related subjects. Radiation is a process where certain energy is radiated from a certain source. Irradiation is a process where radiated energy is incident on a certain surface. The concepts of radiation and irradiation are very important in fields such as physics, waves and vibrations, quantum mechanics, electromagnetic field theory and various other fields. In this article, we are going to discuss what radiation and irradiation are, their applications, definitions of radiation and irradiation, the similarities and finally the difference between radiation and irradiation.


Radiation is a process where energy is released from a surface. Energy can be released from a surface in three ways. The processes of emitting energy from a surface are convection, conduction and radiation. The process of radiation does not require a medium to transfer heat and energy. Radiation is mainly divided into two types. These are electromagnetic radiation and thermal radiation. The properties of these two types of radiation are similar. Only difference between these two types of radiation is the process in which they are generated. Thermal radiation is generated from a thermal source whereas electromagnetic radiation is generated by an oscillation of an electric field and a magnetic field. The energy emission from radiation is quantized. This is known as quantum effect of radiation. A packet of this energy is known as a photon. The energy of this photon depends only on the frequency of the radiation.

The Wien’s law is also a very important law in thermal radiation. The Wien’s law proposes that the temperature of a black body determines the wavelength at which it emits a maximum number of photons.


Irradiation is the process of radiation falling on a surface. Irradiation is a very important phenomenon discussed in physics. Irradiation is very important in phenomena such as the photoelectric effect, Compton Effect, Raleigh scattering and various other events. When a surface is irradiated with radiation, the radiation is either absorbed or reflected. The amount of absorbance or the reflectance from a surface depends on the absorptivity or the reflectivity of the surface. Black bodies absorb all the radiation that is irradiated on the surface. Therefore, the absorptivity coefficient of a black body is equal to one. The absorptivity coefficient and the reflectivity coefficient vary between 0 and 1. The quantity of absorptivity coefficient + the reflectivity coefficient is equal to 1, for any surface.


What is the difference between Radiation and Irradiation?

• Radiation is a noun used to describe a set of photons emitted by a certain source. Radiation is also used as a verb, to describe the process of generating such photons. Irradiation is used only as a verb to describe the process of radiation falling on a surface.

• Radiation can be generated by electromagnetic processes and by heat, as well.

• Radiation of energy from a body always reduces the amount of energy inside the body. Irradiation on a body always increases the amount of energy inside a body.