Difference Between Emission And Absorption Spectra

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Introduction

  • The spectrum is an important concept in order to understand the structure of atoms. The electromagnetic spectrum is an arrangement of all wavelengths ranging from visible light to infrared lights. 

  • Now the visible spectrum is just an impression of particular wavelengths (ranging from 400nm-700nm) when white light is made incident on optical devices like Prism, diffraction grating.

  • The splitting of white light into different wavelengths of colours is known as dispersion and the pattern of colours obtained is a spectrum.


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  • The spectra obtained will be a continuous spectrum, a spectrum is said to be continuous if the pattern obtained doesn’t have distinct spacing between the colours or the wavelengths.

Atomic Spectra:

  • While studying the dual nature of light, we concluded that light behaves like both particle and wave.

  • When the white light interacts with atoms or molecules, it will absorb a certain amount of energy and emits the radiation of different wavelengths resulting in atomic spectra.

  • The atomic spectra further classified into two types:

  1. Emission spectrum

  2. Absorption spectrum

What is Emission Spectrum?

Whenever white light or electromagnetic radiations have interacted with the atoms or molecules, their electrons absorb energy and transit from lower energy level to higher energy levels losing their stability. In order to regain their stability, the electrons will emit energy in the form of radiations.

The radiations emitted by excited electrons will constituent a spectrum of distinct wavelengths known as emission spectra. Since the spectrum obtained is distinct and discontinuous it is also known as a line spectra.


What is Absorption Spectrum?

On the other hand, whenever electromagnetic radiation interact with atoms if their electrons in the ground level jump to an immediate higher energy level will by absorbing energy will result in a continuous spectrum with dark lines, which is known as an absorption spectrum.


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Emission Spectra Vs Absorption Spectra:

The major difference between the emission spectrum and the absorption spectrum is that the absorption spectrum is continuous spectra whereas the emission spectrum is the discontinuous or line spectra.

Let us now look at the main difference between the absorption spectrum and emission spectrum:

Emission Spectra

Absorption Spectra

The emission spectra are obtained due to radiations emitted by excited atoms.

The absorption spectra are obtained when atoms absorb energy.

It is a discontinuous spectrum consisting of a few wavelengths with distinct spacing between them.

It is a continuous spectrum, consisting of all the wavelengths having dark lines between them.

An atom will be having higher energy while exhibiting an emission spectrum.

An atom will be having lower energy while exhibiting an emission spectrum.


These are some important differences between the absorption spectrum and emission spectrum. If the question being asked is the difference between emission spectra and absorption spectra, we should mention a minimum of three differences concluding as emission vs absorption spectra or absorption vs emission spectra.


Fun Facts:

  • Human eyes are most sensitive to a wavelength of 550nm.

  • The visible part of the electromagnetic spectrum is light that the human eye can see.

FAQ (Frequently Asked Questions)

1. What is an Absorption Spectrum? Or What is the Emission and Absorption Spectrum?

Ans: An absorption spectrum is defined as a spectrum obtained due to electromagnetic radiation transmitted through a gas or any substance.

An emission spectrum is defined as a spectrum obtained when atoms absorb energy.

2. Is the Emission Spectrum Continuous? 

Ans:  Yes. Emission spectra are continuous ones.