Write short notes on the Atomic spectra or line spectra.

The spectrum, which plural form is spectra refers to the distribution of energy as a function of wavelength or frequency. Spectra is used to study the structure and composition of matter and provide information about the energies of the atoms and molecules in a sample.

Line Spectra or Atomic Spectra: The spectrum of electromagnetic radiations emitted or absorbed by electrons during the transition between different energy levels is called Atomic Spectra or Line Spectra.

• It consists of sharp and well-defined lines
• It is characteristic of atoms
• It is formed due to the excitation and de-excitation of electrons in the atoms

Atomic Spectra are classified into two types:

1. Emission Spectra or Line Emission spectra
2. Absorption spectra or Line Absorption spectra

Emission Spectra: When an atomic gas or vapor is excited at low pressure by passing an electric current through it, the emitted radiation has a spectrum that contains a specific wavelength, is termed Emission spectra, and consists of bright lines on a dark background.

• It is also known as a line emission spectra.
• The spectrum obtained is distinct and discontinuous.

Absorption spectra: When white light passes through atomic gas or vapor, then the spectrum of transmitted light is observed with a spectrometer showing some dark lines which replaces some bright lines seen in the emission spectrum of the gas. This type of spectra is known as Absorption spectra.

• It is also known as line absorption spectra
• The spectrum obtained is continuous with dark lines

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