Multiple Choice

For an isosceles prism of angle $$A$$ and refractive index $$\mu$$, it is found that the angle of minimum deviation $$\delta_m=A$$. Which of the following option(s) is/are correct?

AAt minimum deviation, the incident angle $$i_1$$ and the refracting angle $$r_1$$ at the first refracting surface are related by $$r_1 = (i_1/2)$$
Correct Answer
BFor this prism the refractive index $$\mu$$ and the angle of prism A are related as $$A = \dfrac{1}{2}\cos^{-1}\left(\dfrac{\mu}{2}\right)$$
CFor this prism, the emergent ray at the second surface will be tangential to the surface when the angle of incidence at the first surface is $$i_1=\sin^{-1}\left[\sin A\sqrt{4\cos^2\dfrac{A}{2}-1}-\cos A\right]$$
Correct Answer
DFor the angle of incidence $$i_1= A$$, the ray inside the prism is parallel to the base of the prism
Correct Answer

Solution

$$Option\ A$$

We know for minimum deviation, $$i_1 = \dfrac{A+\delta_m}{2}$$( $$\delta_m$$ : angle of minimum deviation)
Given $$\delta_m = A$$
Hence $$i_1= A$$
Now, for minimum deviation condition $$r_1 = A/2$$
Hence $$r_1 = i_1/2$$
$$Correct$$

$$Option\ B$$

$$ \mu = \dfrac{sin(i_1)}{sin(r_1)}$$
$$ \mu = \dfrac{sin(\dfrac{A+\delta_m}{2})}{Sin\ (A/2)}$$
$$ \mu = \dfrac{sin\ A}{sin\ A/2}$$ = $$2\ cos\ A/2$$
$$Incorrect$$

$$Option\ C$$

Emergence = $$90^o$$
$$sin\ r_2 = \mu $$
$$r_2 = Sin^{-1}\ \mu$$
Also $$r_1 = A-r_2$$
$$sin i_1 = \mu sin r_1$$
$$sin i_1 = \mu sin (A-r_2)$$
$$sin i_1 = \mu(sinA\ cosr_2-cos\ A\ sinr_2)$$
But $$\mu\ sinr_2=1$$
$$sin\ i_1= \mu\ sinA\ cosr_2-cosA$$= $$sinA\sqrt{4cos^2A/2-1}-cosA$$
$$Correct$$


SIMILAR QUESTIONS

Optics

In an experiment for determination of refractive index of glass of a prism by $$i-\delta\ plot$$ it was found that a ray incident at angle $${ 35 }^{ \circ }$$ suffers a deviation of $${ 40 }^{ \circ }$$ and that it emerges at angle $${ 79 }^{ \circ }.$$ In that case which of the following is closest to the maximum possible value of the refractive index?

Optics

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index:

Optics

The angle of incidence for a ray of light at a refracting surface of a prism is $${45}^{o}$$. The angle of prism is $${60}^{o}$$. If the ray suffers minimum deviation through the prism, the angle of minimum deviation and refractive index of the material of the prism respectively, are

Optics

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index :

Optics

The refracting angle of a prism is A, and refractive index of the material of the prism is cot (A/2). The angle of minimum deviation is :

Optics

The maximum refractive index of a prism which permits the passage of light through it, when the refractive angle of the prism is $${90^0}$$, is

Optics

Calculate the refractive index of glass with respect to water. It is given that refractive indices of glass and water with respect to air are $$\dfrac {3}{2}$$ and $$\dfrac {4}{3}$$ respectively.

Optics

When a ray of light falls on a prism, light gets dispersed because :

Optics

In the condition of minimum deviation position, a ray travels within the prism :

Optics

The refractive index of the material of prism, if a thin prism of angle $$A=6^o$$, produces a deviation $$\delta =3^o$$, is :

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