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What is Spectroscopy?

Spectroscopy is a field of science that deals with the dispersion of an object’s light into its component colours. Astronomers have been able to study the physical properties of objects by analysing object’s light. Moreover, the spectroscopic examination has been critical in the advancement of numerous central hypotheses in Physics.

Usually, one notices two distinct types of spectra: continuous and discrete.  In a continuous spectrum, the light is composed of a broad, continuous range of colours. Contrary to the continuous spectrum, one sees only bright or dark lines at very definite and sharply defined colours with the discrete spectra. Furthermore, discrete spectra with bright lines are known as emission spectrum, those with dark lines are termed absorption spectrum.

Continuous Spectra

Continuous spectra emerge from dense gases or solids that transmit their heat away through light production. Such objects produce light over a broad range of wavelengths. Some examples of such objects are incandescent light bulbs and electric cooking stove burners.

Discrete Spectra

A discrete spectrum is a series of achievable values of a physical quantity, having a positive gap between each value. There are two types of discrete spectra, emission spectrum and absorption spectrum. In the following few sections, let us try to understand each of these spectrum types.

Emission Line Spectra

Unlike a continuous spectrum source, the electrons encompassing the nuclei of atoms can have specific energies. Each element on the periodic table has its own set of possible energy levels. The levels are distinct and identifiable. Atoms tend to descend to the lowest energy lHelloevel. This indicates that an excited atom in a higher energy level must radiate some energy. An atom releases energy by emitting a wave of light with that exact energy.

Absorption Line Spectra

An absorption spectrum arises when an absorbing material is placed between a source and the observer. This material could be the outer layers of a star, a cloud of interstellar gas, or dust. Absorption lines are usually seen as dark lines, or lines of reduced intensity, on a continuous spectrum.Now that we have a brief overview of emission and absorption spectra let us summarise the difference.

Absorption Spectrum Emission Spectrum
They are formed when atoms absorb energy They are formed when atoms release energy
Dark lines or gaps are found in the spectrum Coloured lines are found in the spectrum
The wavelengths of the absorbed light help in figuring out the number of substances in the sample. The emitted radiation helps in figuring out the kind of elements the substance is made of.

 

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