Emission and absorption spectra

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  • Created on: 15-03-16 15:44

Emission and Absorption Spectra

When atoms are given energy by heat or an electric field, electrons are pushed up from a lower energy level to a much higher energy level. We say that the electron is therefore promoted. When the energy source is removed, the electron falls from their high energy level (excited state) to a lower energy level and the energy lost is released as a packet of nergy called a quantum of energy.

Light and Electromagnetic radiation

Light's a form of electromagnetic radiation. It's energy travelling as waves. A wave's described by its frequency (f) and its wavelenegth (λ).

The frequency and wavelength of light are related by the equation:

c = fλ

The frequency of elcetromanetic radiation and energy (E) are connected by the equation:

E = hf

Therefore if frequency increases, energy also increases. If frequency decreases, wavelength decreases.


We're only concerened with inrared, visiblye and ultraviolet regions in this unit. Energy and frequency increase going from the infrared through visible to the ultraviolet region. 

Absorption spectra

Light of all visible wavelengths is called white light. All atoms and molecules absorb lights of certain wavelengths. Thus, when light's passed through the vapour of an element only certain wavelenegths will be asorbed, and others will be removed. Looking through a spectrometer black lines appear where light of


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