AIM

 

To determine the angle of emergence i' for varours angle of incidence i and to draw the i-i' curve.

 

APPARATUS

 

Spectrometer, equilateral prism, sodium light etc.

 

THEORY

 

The graph connecting the angles i and i' is shown in fig(1). The bisector, meets the curve at P.  At the point P, i and i' are equal.

OB = OC = i

The angle of deviation s is given by

      (1)

Where A is teh angle of the prism.

When  i =i' , the deviation is minimum (D).

Hence,

    (2)

Therefore,

    (3)

The regractive index of the prism,

     (4)

Therefore,

     (5)

 Where θ₂ is difference between the reflected ray and direct ray.

 

Spectrometer i-i' curve

 

A graph is drawn with angle of incidence i along X-axis and the angle of emergence i' along Y-axis. The graph is a rectangular parabola. from it, angle of incidence corresponding to minimum deviation is calculated.

                                                                                                                       Fig: 1