About Photons.
A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light. Photons are always in motion and, in a vacuum, travel at a constant speed to all observers of 2.998 x 108 m/s. This is commonly referred to as the speed of light, denoted by the letter c. The energy of a photon is a discrete quantity determined by its frequency given by
E = hυ
where h is plank constant and υ is the frequency of the radiation.
Examples of photons.
1. Characteristic x-ray: Results from electronic transitions between atomic shells.
2. Bremsstrahlung: Results mainly from electron-nucleus Coulomb interactions.
3. Gamma ray: Results from nuclear transitions.
4. Annihilation quantum: (annihilation radiation) Results from positron- electron annihilation.
5. Ultraviolet radiation.
6. Visible light.
7. Infrared radiation (IR).
8. Microwaves.
Photon properties.
The basic properties of photons are:-
— They have zero mass and rest energy. They only exist as moving particles. They are elementary particles despite lacking rest mass.
–They have no electric charge.
–They are stable.
— They are spin-1 particles which make them bosons.
— They carry energy and momentum which are dependent on the frequency.
–They can have interactions with other particles such as electrons, such as the Compton Effect.
— They can be destroyed or created by many natural processes, for instance when radiation is absorbed or emitted.
— When in empty space, they travel at the speed of light.
Facts about photons.
— Not only is light made up of photons, but all electromagnetic energy (i.e.microwaves, radio waves, X-rays) is made up of photons.
— The original concept of the photon was developed by Albert Einstein. However, it was scientist Gilbert N. Lewis who first used the word “photon”
to describe it.
— The theory that states that light behaves both like a wave and a particle is called the wave-particle duality theory.
— Photons are always electrically neutral. They have no electrical charge.
— Photons do not decay on their own.
Creation of Photons.
Photons can be generated in many different ways. This section will discuss some of the ways photons may be emitted. As photons are electric field propagating through space, the emission of photons requires the movement of charged particles.
1. Blackbody Radiation.
2. Spontaneous Emission.
3. Flourescence.
4. Stimulated Emission.
5. Synchrotrons (electron bending).
6. Nuclear Decay.
7. Photoelectric Effect.