What do I know about light?

My understanding of light is as follows:

Light consists of photons. It has only moving mass, but no static mass. In other words, it has been moving. It is motion that gives it energy and momentum, particles like steel balls and waves like sound waves, that is, wave-particle duality. He has no form, just an energy. You can regard him as a small energy.

Only visible light is visible, infrared and ultraviolet rays are invisible. Color is that photons hit the retina, transmitting energy to it, and the dorsal nerve perceives it, so it produces the feeling of light.

The essence of light is electromagnetic waves that can cause vision, and it is also particles (photons).

Light can propagate in transparent substances such as vacuum, air and water. Light speed: The speed of light in vacuum is | 300,000 kilometers per second.

Visible light visible to the naked eye is only a part of the whole electromagnetic spectrum. The visible spectrum of electromagnetic wave is about 390~760nm( 10-9m), and light can be divided into artificial light and natural light.

Light sources are divided into cold light sources and hot light sources; Light source: An object that can emit light by itself is called a light source. Cold light source: it means to emit light without heating (or to generate heat at a very low temperature).

Such as fireflies; Thermal light source: refers to light emitting and heating (must be high temperature heat). Such as the sun; Experiments show that light is electromagnetic radiation, and the wavelength range of this part of electromagnetic wave is about 0.77 micron of red light to 0.39 micron of purple light.

Electromagnetic waves with a wavelength of more than 0.77 micron to about 1000 micron are called "infrared rays". Below 0.39 micron to about 0.04 micron is called "ultraviolet".

Infrared and ultraviolet rays can't cause vision, but the existence of this luminous object can be measured and detected by optical instruments or photography. Therefore, the concept of light in optics can also be extended to infrared and ultraviolet fields. Even X-rays are considered as light, and the spectrum of visible light is only a part of the electromagnetic spectrum.