Lecture 3
ELECTROMAGNETIC
RADIATION
The energy from the natural source, sun is in the
form of electromagnetic radiation (EMR), produced by nuclear reactions within
the sun. The EMR consists of an electric field and magnetic field which are
perpendiculars to each other moving in a-harmonic; wave pattern at: a constant
speed of light (3 x 103 m/s) and perpendicular to the direction of motion.
Electromagnetic
Wave
The electromagnetic wave displays three properties
(Fig. 2.4) (i) Wavelength (ii) Frequency and (iii) Amplitude.
1. Wavelength. It is the length of a single wave
that is from one wave peak to next. It is measured in the unit of length such
as Angstrom (A 10-10 m) Nanometre (nm, 10-9 m),
Micrometer (µm 10-6 m) or Centimetres (cm). It is represented by
Greek letter, Lambda (λ).
2. Frequency. It is measured as number of wave
peaks passing a fixed point in a given time. It is measured in Hertz which is
equal to one cycle / second. It is denoted by v.
3. Amplitude. It is the height of each wave peak.
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