Interference of
light: when two light waves of exactly the same frequency and a constant
phase difference travel in same direction and superimpose then the resultant
intensity in the region of superposition is different from the sum of intensity
of individual waves. This modification in the intensity of light in the region
of superposition is called interference of light. Interference is of two types.
(i)
Constructive interference (ii) Destructive
interference
Constructive
interference: At some points, where the two waves meet is same phase, resultant
intensity is maximum; such interference is called constructive interference.
Destructive
interference: At some points, where the two waves meet in opposite phase,
resultant intensity is minimum. Such interference is called destructive
interference.
Diffraction of light:
When light waves fall on a sized obstacle o a small aperture whose dimension is
comparable to the wavelength of light, then there is a departure from the
rectilinear propagation and light energy flavours out into the region of geometrical
shadow. The spreading of light energy beyond the limit prescribed by
rectilinear propagation of light is called diffraction of light. In other
words, diffraction is the process by which a beam of light or other systems of
wave is spread out as a result of passing through a narrow opening or across an
edge.
Polarization of
light: Polarization is the only phenomenon which proves that light is a
transverse wave. Light is an electromagnetic wave in which electric and
magnetic field vectors vibrate perpendicular to each other and also
perpendicular to the direction of propagation. In ordinary light, the
vibrations of electric field vector are in every plane perpendicular to the
direction of propagation of wave. Polarization is the phenomenon of restricting
the vibrations of a light in a particular direction in a plane perpendicular to
the direction of propagation of wave.
The visible effect of light is only due to electric field
vector.
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