It is characteristic of the absorbing substance.Ībsorption spectra is also of three types. (ii) Absorption spectra: When the light emitted from a source is made to pass through an absorbing material and then examined with a spectrometer, the obtained spectrum is called absorption spectrum. Using band spectra the molecular structure of the substance can be studied.
When the bands are examined with high resolving power spectrometer, each band is found to be made of a large number of fine lines, very close to each other at the sharp edge but spaced out at the other end. Calcium or barium salts in a bunsen flame and gases like carbondioxide, ammonia and nitrogen in molecular state in the discharge tube give band spectra. It is the characteristics of the molecule. (c) Band spectrum: It consists of number of bright bands with a sharp edge at one end but fading out at the other end.īand spectra are obtained from molecules. The substance in atomic state such as sodium vapour lamp, mercury in mercury vapour lamp and gases in discharge tube give line spectra (Fig.)
#Emission spectra line band and continuous free#
It is used to identify the gas.Ītoms in the gaseous state, i.e., free excited atoms emit line spectrum. It is the characteristic of the emitting substance. (b) Line spectrum: Line spectra are sharp lines of definite wavelengths. Incandescent solids, liquids, carbon arc, electric filament lamps, etc., give continuous spectra. These spectra depend only on the temperature of the source and is independent of the characteristic of the source. (a) Continuous spectrum: It consists of unbroken luminous bands of all wavelengths containing all the colours from violet to red. (a) Continuous spectrum, (b) Line spectrum and (c) Band spectrum. Every source has its own characteristics emission spectrum. (i) Emission spectra: When the light emitted directly from a source is examined with a spectrometer, the emission spectrum is obtained.
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