Question

What are Fraunhofer lines? What is their importance?

Answer 1

Hint: These are the lines which are produced due to absorption of definite wavelengths by some atoms when sunlight passes through the different gases present in the atmosphere.

Complete step by step answer:
The Fraunhofer lines are the dark absorption lines in the spectrum of stars. It is a set of spectral lines which is caused by the selective absorption at specific wavelengths of a star’s radiation. It was first observed by an English physicist William Hyde Wollaston in 1802 but named after a German physicist Joseph von Fraunhofer. There are various gases present in the atmosphere, when sunlight consisting of white light passes through these gases, some colours get missing when it emerges from these gases. This happens because different atoms absorb light of definite wavelengths. There are continuous black lines in the spectrum. These black lines are called Fraunhofer lines. There are about 25,000 Fraunhofer lines now known to exist in the solar spectrum whose wavelengths lie between \[2950\mathop A\limits^0 \] and \[10000\mathop A\limits^0 \].

Note:
There are three types of spectrum: Continuous, Emission, Absorption.
In continuous spectrum all the colours of white light are visible when passed through a prism.
In the emission spectrum different lights of different wavelengths are produced when passed through a gas. This happens due to the different energy levels of different atoms in an excited state. When an atom or a molecule jumps from a high energy level to a low energy level. Emission spectrum takes place.
In the absorption spectrum some particular wavelengths of definite colours are missing when white light is allowed to pass through a gas.