Light

Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. The three basic dimensions of light (i.e., all electromagnetic radiation) are:

Color and wavelengths

The different wavelengths are detected by the human eye and then interpreted by the brain as colors, ranging from red at the longest wavelengths of about 700 nm. (lowest frequencies) to violet at the shortest wavelengths of about 400 nm. (highest frequencies). The intervening frequencies are seen as orange, yellow, green, cyan, blue, and, conventionally, indigo.

Related Topics:
Brain - Red - Violet - Orange - Yellow - Green - Cyan - Blue - Indigo

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The wavelengths of the electromagnetic spectrum immediately outside the range that the human eye is able to perceive are called ultraviolet (UV) at the short wavelength (high frequency) end and infrared (IR) at the long wavelength (low frequency) end. Although humans cannot see IR, they do perceive the near IR (shorter wavelength, higher frequency, higher energy) as heat through receptors in the skin. Cameras that can detect IR and convert it to light are called, depending on their application, night-vision cameras or infrared cameras (not to be confused with an image intensifier that only amplifies available visible light).

Related Topics:
Ultraviolet - Infrared - Near IR - Heat - Skin - Camera - Night-vision - Infrared camera - Image intensifier

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UV radiation is not directly perceived by humans at all except in a very delayed fashion, as overexposure of the skin to UV light can cause sunburn, or skin cancer, and underexposure can cause depression due to vitamin D deficiency. However, because UV is a higher frequency radiation than visible light, it very easily can cause materials to fluoresce visible light.

Related Topics:
Sunburn - Skin cancer - Depression - Vitamin D - Fluoresce

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Some animals, such as bees, can see UV radiation while others, such as pit viper snakes, can see IR using pits in their heads.

Related Topics:
Bee - Snake

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