Principle of Superposition of Waves: When two or more
waves, travelling through a medium, arrive at a
point of the medium simultaneously, each wave produces its own displacement
at that point, independently of the other wave.
Interference of Light: The redistribution of intensity of
light due to the superposition of the waves of light. It was discovered by
Thomas Young in 1801.
Coherent Sources: Sources that emit light with constant phase
Monochromatic Light: Light consisting of one wavelength.
Fringes: The alternate bright and dark bands in an interference
Band Width: The width of an adjacent dark and bright
band. The distance between two consecutive dark or bright bands.
Biprism: A system of two
prisms attached base to base and having very small refracting angle.
Path difference (Dx) and Phase
difference (Df): They are related by the equation Df =
Constructive Interference: If two waves of
light, arriving simultaneously at a point, are in phase, the crest due
to one wave coincides with the crest due to the other and the trough due to
one wave coincides with the trough due to other. Therefore, the resultant
displacement and hence the resultant intensity of light at that point is maximum
and the point is bright. This phenomenon is called constructive
Destructive Interference: If two waves of
light, arriving simultaneously at a point, are in opposite phase, the
crest due to one wave coincides with the trough due to the other and vice
versa. Therefore, the resultant intensity at that point is minimum
and the point is dark. This phenomenon is called destructive