**Displacement of Fringes, Fringes, Interference of Fringes, Interference of Light**

**DISPLACEMENT OF FRINGES**

If a thin glass or mica
strip or any other transparent plate of uniform thickness is introduced in the
path of one of the two interfering beam from two coherent sources then central
bright fringe will be displaced. This displacement from C to C00 will towards
the side of lamina.

In order to calculate
the displace we shall find the path difference between two beam from coherent sources
S1 and S2 at any point ‘P’ on the screen. Let ‘t’ be the thickness of sheet and
‘μ’ the refractive index
of its materials.

Time T taken by the
beam to reach from S1 to P is given by

where
C is the velocity in air and V is velocity of light in the medium of the plate

The condition for
maxima

If P is the centre of
the nth bright fringe

**Shift of Central Fringe**

This
expression is independent of n. This indicate that all the bright fringes are
displaced through the same amount equal to
similarly it can be shown that the
displacement of any dark fringe is also

The fringe width ω is given by

## No comments:

## Post a Comment