Electromagnetic Wave Theory (Maxwell)

The energy is emitted from source continuously in the form of radiations and magnetic fields. All electromagnetic waves travel with the velocity of light (3 * 108 m / s) and do not require any medium for their propagation.
An electromagnetic wave has the following characteristics:
(i) Wavelength It is the distance between two successive crests or troughs of a wave. It is denoted by the Greek letter λ (lambda).
(ii) Frequency It represents the number of waves which pass through a given point in one second. It is denoted by v (nu).
(iii) Velocity (v) It is defined as the distance covered in one second by the waves. Velocity of light is 3 * 1010 cms-1
(iv) Wave number It is the reciprocal of wavelength and has units cm-1 It is denoted by v (nu bar).
(v) Amplitude (a) It is the height of the crest or depth of the trough of a wave.
Wavelength (λ), frequency (v) and velocity (c) of any electromagnetic radiations are related to each other as c = vλ
Electromagnetic Spectrum
The different types of electromagnetic radiations differ only in their wavelengths and hence. frequencies. When these electromagnetic radiations are arranged in order to their increasing wavelengths or decreasing frequencies, the complete spectrum obtained is called electromagnetic spectrum.