Prism Formula

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics:

Prism Formula:

If the angle of incidence is increased gradually, then the angle of deviation first decreases, attains a minimum value(δm) and then again starts increasing.

Note: From graph it is clear that(experimentally).
1. Angle of deviation is minimum for only one value of angle of incidence.
δ→δmin,  then i= e and r₁=r₂=r.

2. This is not a parabola.

3. For each δ(except δmin) there are two value of i.

Prism Formula

This relation is called a Prism formula.

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