Question

If angle of deviation through a prism of angle 60° is 40°, angle of incidence (being equal to angle of emergence) would be:

a) 50°
b) 60°
c) 40°
d) None of these​

Answer 1

Explanation:

Correct option is

A

50o

For minimum deviation i=ei=e

a+δm=i+ea+δm=i+e

a+δm=2ia+δm=2i

60o+40o=2i

i=50o

Answer 2

Given:

Angle of prism ( A ) = 60°

Angle of deviation ( δ ) = 40° ; and

Angle of incidence ( i ) = Angle of emergence ( e )

To find :

Angle of incidence ( i )

Explanation :

• The relation between angle of incidence (i), angle of emergence (e) , angle of prism (A) and angle of minimum deviation (δ) when light passes through a glass prism is given by,

                                        i + e = A + δ

Solution :

Since it is given that, i = e

therefore, 2 i = A + δ

Substituting the given values, we get

                 2 i = 60° + 40°

therefore,     i = 50°

Final answer :

Hence, the value of Angle of incidence (i) is option (A) 50°.