Laser
Character of light
Light has the character of the diffraction and interference.
It was thought that the substance of light was a wave.
Einstein designed the photon hypothesis, and it is understood also that light is a particle and wave motion today.
The example of the character as the wave of light is refraction, a diffraction, and interference. The phenomenon that happens because of the character as the particle is a photoelectric effect.
The electromagnetic radiation is a wave where the electric field and the magnetic field are alternately transmitted. The electric wave, light, X rays, and gamma rays are all electromagnetic radiations respectively though wavelength is different them.
The electromagnetic radiation within the range of wavelength about 0.4-0.8ƒÊm is visible light. The side where wavelength is long is and there is red. It changes with the bitter orange, yellow, green, blue, indigo, and purple as wavelength shortens. The difference of the color is a difference of wavelength.
When the sun light is seen through the prism, it resolves it like hues of a rainbow. In a word, various wavelength mixes with the sun light. Not only the sun light but also a lot of light in the world is various light with which various wavelength mixes. Light in such a state is said that monochromaticity is bad.
The electromagnetic radiation of wavelength that is longer than the range of visible light is infrared rays and an electric wave. When it is shorter than the range of visible light, it becomes ultraviolet rays, X rays, and gamma rays.
The refractive index of light is different depending on wavelength. If various light is passed through the prism, the light of each wavelength can be separated. In a word, the light only of specific wavelength can be picked up. The light only of single wavelength is called monochromatic light.
The phase is asunder though wavelength becomes complete in the monochromatic light picked up with the prism. The state of such light is expressed, can "incoherent".
The ray diffuses to a general source of light such as lamps. The light that occurred from the source of light extends in all directions. The index how the ray goes straight is called a directivity. The directivity of a general source of light is bad.
In light, each character of monochromaticity, coherent, and the directivity is equipped. As for the sun light and the light, these characters are not excellent. The technology that generated an excellent in monochromaticity, coherent, and the directivity artificial rays was invented by using the stimulated emission of the atom in 1960's. Such artificial light is called laser light.
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