Types of Spectra

Diffraction gratings are made by etching parallel lines very close together on a smooth glass plate.There are three types of spectra: continuous, line emission and line absorption spectra.Light from a filament lamp is a continuous spectrum. A range of wavelengths of light from deep violet at about 350nm to red at about 650nm is emitted. The hotter the filament, the shorter peak or brightest wavelength so this can be used to determine the temperature.Visible light is produced when excited electrons fall to a lower energy level. Visible light from a vapour lamp or discharge tube only consists of specific wavelengths of visible light. The wavelengths are characteristic of the element that produced the light and this will form a line spectrum in the form of coloured lines on a screen..Absorption spectra are continuous spectra with black lines at the characteristic wavelengths absorbed. If light from a filament lamp is passed through a glowing gas, the black lines observed are at the same characteristic wavelengths of the element in the gas.