What is untraviolet and infrared spectrum?

Ultraviolet and Infrared Spectrum

When an object is suitably excited by heating or i some other way, it emits light. The light, that causes visual sensation to the eye, has a wavelength range from about 380 nm to about 780 nm. The light emitted by an excited object may have wavelengths beyond this visible region. We generally use the word light to mean visble light. That beyond the visible region is called by the general name radiation. The radiation with wavelength less than the lower end of the visible region is called ultraviolet radiation and the radiation with the wavelength greater than the upper end of the visible region is called the infrared radiation. The range of ultraviolet radiation is roughly from 15nm to 380 nm and that of infrared radiation is roughly 780 nm to 40000 nm. Beyond untraviolet, we have X - rays and gamma - rays and above infrared, we have radiowaves.

Ordinary glass highly absorbs infrared and ultraviolet radiation. A prism made of quartz may be used for studying the spectrum in ultraviolet region. The dispersed radiation may be collected on a photographic plate. To study infrared spectrum, one can use a prism made of rocksalt. Infrared radiationconsiderably hetas the object on which it falls. One way of detecting infrared radiation is from its ehating effect. An instrument known as thermopile, which is sensitive to heat, is used to measure the dispersed infrared spectrum.

w