Answer: Electromagnetic radiation consists of oscillating electric and magnetic fields and is described by its wavelength, frequency, wave number, velocity, amplitude and energy.
Nature: the electric and magnetic fields oscillate perpendicular to each other and to the direction of travel. The radiation needs no medium and travels in vacuum with the same speed \(c = 3\times10^{8}\ \mathrm{m\,s^{-1}}\).
- Wavelength (\(\lambda\)): distance between two successive crests or troughs; units m, cm, nm, Å.
- Frequency (\(\nu\)): number of waves passing a point in one second; unit Hz (s−1).
- Velocity (\(c\)): distance travelled by the wave in one second, related by \(c = \nu\lambda\).
- Wave number (\(\bar{\nu}\)): number of waves per unit length, \(\bar{\nu} = 1/\lambda\); unit cm−1 or m−1 (widely used in IR spectroscopy).
- Amplitude: height of the crest or depth of the trough; it decides the intensity of the radiation.
- Time period (\(T\)): time for one complete wave to pass a point, \(T = 1/\nu\).
- Energy: radiation is emitted and absorbed in packets (photons) of energy
\[E = h\nu = \frac{hc}{\lambda} = hc\bar{\nu}\]
where \(h = 6.626\times10^{-34}\ \mathrm{J\,s}\). So shorter wavelength (higher frequency) means higher energy.
