Difference Between Emission And Absorption Spectra

Dhristi JEE 2022-24

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 colors is known as dispersion and the pattern of colors obtained is a spectrum.


(Image Will Be Uploaded Soon)


  • 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 colors or the wavelengths.


Atomic Spectra:

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

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

  • The atomic spectra are further classified into two types:

  1. Emission spectrum

  2. Absorption spectrum


What is Emission Spectrum?

Whenever white light or electromagnetic radiation 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 radiation.


The radiation emitted by excited electrons will constitute 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 interacts with atoms, if their electrons in the ground level jump to an immediate higher energy level, absorbing energy will result in a continuous spectrum with dark lines, which is known as an absorption spectrum.


(Image Will Be Uploaded Soon)


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:


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.


Applications of Emission and Absorption Spectra

Spectroscopy is a branch of science used in astronomy to study the spectra of light from stars and galaxies. It is an important science branch in astronomy that helps to study different astronomical objects.

It helps to identify elements in the astronomical object by studying their spectra.

Astronomers can measure the spectrum of light from a star to know the elements of the star. Each element emits light at a particular wavelength, therefore astronomers can find out what elements made up the stars from their lines in the spectra. 

It helps in finding the velocities of galaxies

When the object that emits light is moving towards us, the wavelength of the light will look shorter and if the object is moving away from us, the wavelength of light will appear longer. This concept is used in finding the velocities of galaxies. The light moving away from us from a distant galaxy will appear longer and it helps astronomers in measuring the velocity of galaxies.


Global Warming

The sun emits radiations at different wavelengths that are seen in the visible spectrum. The radiations emitted by the sun pass through the atmosphere and warm up the land and oceans. The warm land also radiates the heat at longer wavelengths. Carbon dioxide has energy levels corresponding to the infrared wavelengths that help to absorb the infrared radiations of the sun. Therefore, it also emits infrared wavelengths in all directions which heats up the atmosphere. More radiations are coming into the atmosphere than getting out. This is the reason for the greenhouse effect and rising temperature on the earth's surface. 


This could be very harmful to living organisms because it can disturb the balance. Rising temperature can result in the melting of the ice from glaciers and can lead to floods in many parts of the earth. Thus, we should be careful and should take steps to stop this.


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.

FAQs on Difference Between Emission And Absorption Spectra

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

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? 

Yes, Emission spectra are continuous ones.

Comment