|
|
UV rays are an invisible form of light. They lie just beyond the violet end of the visible spectrum. The sun is major source of ultraviolet rays. Lightning,or any other electrical spark in the air, also emits ultraviolet rays. The rays can be produced artificially by passing electric current through a gas or vapour, such as mercury vapour. Ultraviolet rays can cause sunburn. Overexposure to these rays can cause skin cancer. Ultraviolet rays also destroy harmful organisms and have other effects.
The wavelength of ultraviolet rays determines whether a material they shine on absorbs the rays or transmits them. For example, only ultraviolet rays with large wavelengths can pass through ordinary window glass. The glass absorbs rays with shorter wavelengths, though they can pass through other materials.
Infrared rays are often called heat rays, resemble light rays, but they cannot be seen by human eye.They are a form of electromagnetic radiation and behave similarly to light rays in both reflection and refraction any object, such as chair gives infrared radiation in relation to temperature.
Photographers use films that are sensitive by the infrared rays to take pictures which are sensitive. Doctors use infra red lamps to treat the skin diseases and in some muscle treatment, the infra red rays passes through the patients skin and produce heat when they strike their affected area.
Infrared rays lies just beyond the visible light spectrum. Sir William Herschel, a British astrnomer, discovered infrared rays in 1800 by observing the effect of the heat they produced. Infrared rays are often called heat rays, resemble light rays, but they cannot be seen by human eye. They are a form of electromagnetic radiation and behave similarly to light rays in both reflection and refraction.