2016 May

Emission and Absorption Spectra Explained

May 13, 2016

Absorption, Emission and Continuous Spectra

The word ‘Spectrum’ typically refers to the electromagnetic spectrum which consists of all the electromagnetic radiation frequencies. Previously, the term was limited to light only, but afterwards, it was revised to incorporate other waves, like the sound waves. The range of wavelengths is from a pico-meter to thousands of mega-meters. It contains the visible spectrum in its range, which incorporate all the visible wavelengths, to naked eye. Other radiation types include gamma rays, radio waves, X-rays and many more.

Other types of spectra include; energy spectrum, frequency spectrum, mass spectrum, and so forth. The most important spectra are the absorption spectrum and emission spectrum. There are a number of differences between absorption spectrum and emission spectrum, besides the loss or uptake of energy.

The Fundamentals

When energy is given to an element in the form of heat, chemical agents, or light, electrons of the element’s atoms accept this energy and move to higher energy levels. On the other hand, these electrons will have to release energy for them to return to their ground states, considering that the excited state is unbalanced. The light frequencies produced in such a case includes the emission spectrum. Once an electron moves down to the ground state from an excited state, it emits an energy photon. This photon’s energy is depended on the variation of energy between the energy levels of these two states.

As we have learnt during our Physics tuition classes on Quantum Physics, when in the ground state, electrons may take in incident energy for them to attain a higher energy state. The light frequencies transmitted via this substance, having dark bands displaying the absorbed light, makes the substance’s absorption spectrum.

Emission is the process in which a substance gives off radiation when it’s treated chemically or heated. A substance’s emission level depends on temperature and its spectroscopic composition. On the other hand, absorption is the process in which a substance’s electrons take up or simply absorb the energy wavelengths given to them. The material’s molecular and atomic structures determines its absorption level, as well as the solid crystal structure, amount of electromagnetic radiation, inter-molecular interactions, and temperature.

The emission spectrum of a given gas is denoted by an assortment of separate colored lines, which have dark spaces in between them. These lines are the spectrum’s parts where emission take place, while at the dark spaces is where no emission is occurring, hence the darkness. The colors’ difference is due to the electrons’ energy levels variation. On the other hand, an element’s absorption spectrum is represented by use of a continuous band of colors which have distinct dark lines in between them.

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