Question

for a ray of light to pass symmetrically through a prism of refracting angle 60 degree and n=1.6 the angle of incidence must be

Answer 1

$\huge{\textbf{\underline{Explanation:-}}}$

$\textbf{\underline{\underline{As per given Condition:-}}}$

Refracting angle of prism = 60°

Refractive index = 1.6

We have to find :-

Angle of incidence.

$\textbf{\underline{Solution:-}}$

• By using Second law of refraction.

"The ratio of sine angle of incidence to the sine angle of refraction is constant for a given pair of media".

• This law is also know as Snell's law.

$\textbf{\underline{By using the above law :- }}$

$\dfrac{Sin i }{Sin r} = n$

Where n is refractive index of medium.

$\dfrac{Sin i}{Sin60^{\circ}} = 1.6$

$\dfrac{Sin i}{\dfrac{\sqrt{3}}{2}} = 1.6$

$\dfrac{2Sin i}{\sqrt{3}} = 1.6$

$2 Sin i = 1.6 \times \sqrt{3}$

$Sin i = \dfrac{1.6 \times \sqrt{3}}{2}$

$Sin i = 1.3855$

$Sin i= 1.3855$

• Value is close to 1.

$Sin i = Sin 90^{\circ}$

$I = 90^{\circ}$

hence,

Angle of incidence will be 90°.