Electromagnetic Radiation Spectrum Diagram
Electromagnetic spectrum radiation diagram and chart represents the number of radiation spectra formed by the electrical field and magnetic field. Thus each type of electromagnetic spectrum radiation like radio waves, ultraviolet (UV), infrared (IR), visible rays of light has a definite energy, frequency, and wavelength.
Quanta or photons can describe the particle properties, but the wave properties describe by spectrum wavelength and frequency.
Wavelengths of the Electromagnetic Spectrum
The wavelength provides a distance between two consecutive waves. Hence the wavelengths of the electromagnetic spectrum are express in either meters, millimeters, micrometers, or nanometers.
In addition to wavelength, the radiation also expressed in frequency. Therefore the frequency of spectrum is defined as the number of complete cycles per second (cps) and also called Hertz according to the name of German physicist H.R Hertz.
Wavelength Frequency and Energy
From the definition wavelength and frequency, wavelength are inversely proportional to frequency.
where c = 3 × 1010 cm sec-1 = velocity of light.
But de Broglie provides a direct relation between the frequency wavelength and energy of electromagnetic waves.
E = hν = hc/λ
where h = Plank constant
Therefore according to the relation, the frequency is very high or wavelengths are very short, the energy of the atomic spectra also high. For example, X- rays are more energetic than visible light.
Electromagnetic spectrum chart
The electromagnetic spectrum chart flows from cosmic rays to the microwaves spectrum but the visible radiation flows from waves 400 nm (violet) to 750 nm (red light).
|Cosmic rays||5 × 10-5 nm|
|Gamma rays||10-3 – 15 nm|
|X – rays||0.01 – 15 nm|
|Far UV||15 – 200 nm||666,667 to 50,000 cm-1|
|Near UV||200 – 400 nm||50,000 to 20,000 cm-1|
|Visible||400 – 800 nm||25,000 to 12,500 cm-1|
|Near IR||0.8 – 2.5 μ||15,500 to 4000 cm-1|
|Vibrational IR||2.5 – 25 μ||4,000 to 400 cm-1|
|Far IR||0.025 – 0.5 nm||400 to 200 cm-1|
|Microwave||0.05 – 300 nm||200 to 0.033 cm-1|
From the above wavelength chart, the visible region of spectra contains a very small part of the entire spectrum. Thus the waves of the visible region slightly higher than IR radiation and slightly lower than the ultraviolet spectrum.
Electromagnetic Energy and Wavelength
The energy and wavelength of the electromagnetic spectrum are different for different substances. When the energy of light does not match, then the light is not absorbed by the substances. Therefore the spectra provide the most important physical properties of inorganic and organic compounds.
Therefore spectroscopy is an important tool for structure determination. Thus absorbed energy of electron brings the substances in different kinds of excitation.
- The ultraviolet and visible light bring the valence electrons from lower energy levels to higher energy. Hence the UV-visible light frequency changes in electronic energy levels to forms the atomic spectra in the molecules.
- IR spectroscopy causes vibrational excitation among the molecules. Thus IR spectroscopy changes the vibrational and rotational movements of the molecules.
- But microwave forms NMR spectroscopy in the molecules. It affects rotation around the chemical bond of the molecules.