Electromagnetic radiation in Spectroscopy
It was believed that light travels in a straight line. But this concept could not explain some important phenomena like interference, refraction, diffraction etc .To explain these phenomena, light is supposed to travel in a waves . visible light is a form of energy. It can be explained by two complimentary theories, the corpuscular theory and the wave theory. All the properties of light can be explained by considering both the theories. According to the wave theory, light travels in the form of waves. It was believed that radiant energy is emitted by fluctuation of electric charge and the magnetic field. Like light. There are various forms of electromagnetic radiations such as Ultra-violet, Infra-red, X-rays, Radio-waves etc.
These are produced by the oscillation of electric charge and magnetic field residing on the atom. The electic and magnetic components are mutually perpendicular to each other.
The energy carried by an electromagnetic radiation is directly proportional to its frequency. The emission or absorption of radiation is quantised and each quantum of radiation is called a photon
When visible light (a group of electromagnetic radiations) is passed through a prism, it is split up into seven colours which correspond to definite wavelengths. This phenomenon is called dispersion.
The study of spectroscopy deals with emission as well as absorption spectra. When electric discharge is passed through the vapour of the substance, energy is absorbed and electrons in the ground state are promoted to meta-stable state. When electrons from the meta stable state jump to the lower energy state, then some energy of definite frequency is emitted as radiation. The wavelengths which are absorbed characterised some particular functional groups present in the compound or the compound itself in absorption spectrum. The absorbed energy may heat up the sample or is re-emitted.
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