Emission vs Radiation
We are surrounded with radiation and radiation emitting sources in our environment. Sun is the most important radiation emitting source that we all known of. Every day we are exposed to radiation, which are not harmful or sometimes, harmful to us. Except the harmful effects, there are many benefits from radiation for our lives. Simply, we see everything around us because of radiation emitting from those objects.
What is Radiation?
Radiation is the process where waves or energy particles (e.g.: Gamma rays, x-rays, photons) travel through a medium or space. The unstable nuclei of radioactive elements are trying to become stable by emitting radiation. Radiation can be either ionizing or non-ionizing. Ionizing radiation has high energy, and when it collides with another atom, it will be ionized, emitting another particle (e.g. an electron) or photons. The emitted photon or particle is radiation. The initial radiation will continue to ionize other materials until all its energy is used up. Alpha emission, beta emission, X-rays, gamma rays are ionizing radiations. Alpha particles have positive charges, and they are similar to the nucleus of a He atom. They can travel across very short distance. (i.e. few centimeters). Beta particles are similar to electrons in size and charge. They can travel a longer distance than alpha particles. Gamma and x-rays are photons, not particles. Gamma rays are produced inside a nucleus, and x-rays are produced in an electron shell of an atom.
Non ionizing radiations do not emit particles from other materials, because their energy is lower. However, they carry enough energy to excite electrons from ground level to higher levels. They are electromagnetic radiation, thus have electric and magnetic field components parallel to each other and to the wave propagation direction. Ultra violet, infra red, visible light, microwave are some of the examples to non ionizing radiation. We can protect ourselves from harmful radiation by shielding. The type of shielding is determined by the energy of the radiation.
What is Emission?
Emission is the process of releasing radiation. When atoms, molecules, or ions are in the ground state, they can absorb energy and go to an upper excited level. This upper level is unstable. Therefore, they tend to release the absorbed energy back and come to the ground state. The energy released or absorbed is equal to the energy gap between the two states. When releasing energy as photons, they can be in the range of visible light, X- ray, UV, IR, or any other type of electromagnetic wave depending on the energy gap of the two states. The wavelengths of the emitted radiation can be determined by studying the emission spectroscopy. Emission can be of two types, spontaneous emission and stimulated emission. Spontaneous emission is the one described previously. In stimulated emission, when an electromagnetic radiation interact with matter, they stimulate an electron of an atom to drop to a lower energy level releasing energy.
What is the difference between Radiation and Emission?
• Emission is the act of giving radiation. Radiation is the process where these emitted photons travel through a medium.
• Radiation can cause emission when it interacts with matter.