Question

when a ray is refracted through a prism then (1) angle i =angle d (2) angle i =angle e+angle d (3) angle d=angle e (4) angle i greater than angle r​​

Answer 1

Answer:

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

2

3

and refracting angle 90

o

. Find the minimum deviation produced by prism.

Solution:

At minimum deviation, r

1

=r

2

=A/2=45

∘

And, i=e=sin

−1

(

2

3

)=60

∘

δ

min

=i+e−A=30

∘

MINIMUM ANGLE OF DEVIATION FOR A PRISM - DEFINITION

At the minimum deviation D

m

, the refracted ray inside the prism becomes parallel to its base.

i.e i=e⇒r

1

=r

2

=r

Then r=

2

A

and D

m

=2i−A

where i is the angle of incidence,

e is the angle of emergence.

r

1

,r

2

are the angles of refraction and A is the angle of the prism.

Answer 2

When a ray is refracted through a prism then i + e= A + δ

• When a ray of light passes through a glass prism, the relation between the different angles formed by the refracted ray is as follows:

                                           i + e = A + δ

Where,

i = Angle of incidence

e= Angle of emergence

A = Angle of prism

δ = Angle of deviation

• In the case of minimum deviation, angle of incidence= angle of emergence, that is i = e
• In this case, angle i = (A + δ)/2