What is light? The concept of light

The basic concept of light is electromagnetic wave. The wavelength range of 380 ~ 760nm electromagnetic wave can make human eye perception, this part of the electromagnetic wave is called visible light; a wavelength longer than 760nm infrared, radio frequency and wavelength less than UV and X ray 380nm cannot cause the human visual reaction. All visible light is mixed together to form a daylight (white light) relative to the spectral light as part of the electromagnetic wave, which can be measured. However, experience and experiments have proved that different wavelengths of visible light in the eyes of people with different light perception. Even though the energy of visible light at different wavelengths is the same, the brightness is different. Generally speaking, the human eye is most sensitive to the wavelength of 555nm yellow green light. The farther the wavelength is from the 555M, the lower the sensitivity of the human eye to the photoreceptor. The amount of visual power that is used to measure electromagnetic waves, called spectral luminous efficiency. The ratio of the visible light spectral efficiency and the spectral luminous efficiency of 555nm visible light at any wavelength.