Light

The frequency of the electromagnetic wave is 10¹⁴ to 10¹⁵ Hz and the velocity of light in vacuum is c = 299792485 m/sec which was determined in 1983. The origin of their generation can be categorized as follows:

Black body radiation (high temperature object)

Transition of energy states (LED, laser, fluorescence, etc.)

Bramstrahlung (decelerated electrons)

Synchrotron radiation (electrons of circular motion with high speed)

Cherenkov radiation (moving charged particles with velocity larger than c/n, n: refractive index of medium, etc.)

γ (Gamma) decay