Relation Between Angle of Prism and Angle of Deviation, Refractive Index of Materials
Factors affecting the angle of deviation
Angle of deviation depends on:
Angle of incidence i.
Material of prism i.e. μ.
Angle of prism A.
Colour of wavelength used λ.
Calculate angle of minimum deviation of light ray passing through prism
The Angle of Deviation is the angle equal to the difference between the angle of incidence and the angle of refraction of a ray of light passing through the surface between one medium and another of different refractive index.
Example: A prism has a refractive index 23 and refracting angle 90o. Find the minimum deviation produced by prism.
Solution: At minimum deviation, r1=r2=A/2=45∘ And, i=e=sin−1(23)=60∘ δmin=i+e−A=30∘
Minimum angle of deviation for a prism
At the minimum deviation Dm, the refracted ray inside the prism becomes parallel to its base. i.e i=e⇒r1=r2=r Then r=2A and Dm=2i−A where i is the angle of incidence, e is the angle of emergence. r1,r2 are the angles of refraction and A is the angle of the prism.
Terms related to prism
Angle of prism: The angle between the two sides of the reflecting faces of prism is called angle of prism. Angle of deviation (δ): Angle between the incident ray and the emergent ray is called the angle of deviation.
Factors affecting on angle of deviation
Angle of deviation (δ) is the angle between emergent ray and incident ray. δ=(μ−1)A