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Visible light and invisible radiation

From ultra violet to infra red

The human eye can detect electro magnetic radiation with wavelengths between 380 to 780 nanometer. The wavelength is the distance between the highest points in the wave. One nanometer is a billionth of a meter. Light travels in air with approximately 300 000 km per second.

When light is refracted (i. e. through a lens), white light is devided in all colours of the rainbow. This phenomenon is called colour dispersion. The colour dispersion varies from different materials and also the power of the lens etc.

The colour dispersion shows us that white light actually consists of all wavelengths from the energetic blue light with short wavelengths to the long wave red light.

The visible light consists of light with wavelengths from 380 to 780 nanometer, next to visible light is ultra violet and infra red. When all wavelengths is mixed, we interpret the light as white.

The harmful UV light

The harmful UV light has a wavelength of shorter than around 400 nanometer. The visible blue light with short wavelength can also be harmful for the eye, both the anterior parts and the retina. It has been shown that high exposure of UV light is increasing the risk of developing macular degeneration.

The optical parts of the eye (cornea and crystalline lens) is refracting the light to a sharp image on the retina. The pupil is regulating how much light to let in to the eye, serving as an aperture on a camera. This complicated process, we are trying to influence and cooperate with different kinds of filter lenses.

Infra red light in everyday life

The invisible infra red radiation does not have the same negative effects on the eye. It is commonly used in different machines such as remote controls. It is also used in night vision goggles and optical measuring devices.