*optical bench

* biprism

*Convex lens

*Sodium vapour lamp

*Slit

*Micrometer eyepiece

λ = βd

D

where,

λ – wavelength of light,

β – fringe width,

d- the distance between two virtual sources formed by biprism,

D- the distance between the slit and the eyepiece.

Slit ( source)

Biprism ( two virtual souse)

Stand for lens

Optical bench

Whole setup foe deterring the wavelength of sodium ligh by Fresnel's biprism

Whole setup for determining the diameter of wire by using difrraction in shadow region phenomenon:-

source

slit

Stand for wire

Screen or eyepiece

Screw to setup the slit axis ( i.e. parallel to wire)

Slit opening

Screw to adjust the width of the slit

Screw to adjust the height of the slit

SLIT:-

Screw to adjust the axis of Biprism

Screw to inset the Biprism properly

Biprism

Screw to adjust the height of the biprism

Tangent screw (to remove the lateral shift of the fringe pattern).

Biprismstand:-

Screw to adjust the axis of the wire

Wire to measure the diameter

Screw to fit the wire stand

Optical bench

Tangent screw.

Wire Stand:-

Micrometer reading

Screw to rotate the micrometer

Ramsden’s eyepiece( screen to see the fringes)

Main scale reading

Screw to adjust the upright position of screen.

Screen:-

To remove the bench error:-

slit Measuring rod

stand

How to remove the bench error:-

first of all measure the length of rod by optical bench and by scale both.

scale measure the actual length and optical bench measure the apparent one.

then find the error.

Precautions:-

Always first remove the lateral shift then onwards perform the experiment.