Tag: optics

Questions Related to optics

Three right angied prisms of refractive indices $\mu _1$,$\mu _2$ and $\mu _3$ are joined together so that the faces of the middle prism are each in contact with one the outside prism.If the ray passes through the composite block undeviated,then

  1. ${\mu _1}^2+{\mu _3}^2-{\mu _2}^2 = 1$

  2. ${\mu _1}^2-{\mu _3}^2+{\mu _2}^2 = 1$

  3. ${\mu _1}^2-{\mu _3}^2-{\mu _2}^2 = 1$

  4. ${\mu _2}^2+{\mu _3}^2-{\mu _1}^2 = 1$


Correct Option: A

Total reflecting prisms are _____ prism.

  1. Right angled

  2. Acute angled isosceles

  3. Right angled isosceles

  4. Obtuse angled isosceles.


Correct Option: C
Explanation:

Total reflecting prism are right angled isosceles prism with $90^{o}$ between two refracting surfaces.

An equilateral prism deviates a ray through $45^{\circ}$ for the two angles of incidence differing by $20^{\circ}.$ The angle of incidence is

  1. $62.5^{\circ}$

  2. $42.5^{\circ}$

  3. Both are correct

  4. Both are wrong


Correct Option: C
Explanation:

First angle of incidence $=i _1=i$

Second angle of incidence $i _2=i _1+20^\circ$
Angle of deviation, $d=i _1+i _2-A$ where A is angle of prism.
$45=2i+20-60$
$i=42.5$
$i _2=i+20=62.5$
Hence both are correct.

A light ray is incident normally on one of the refracting faces of a prism and just emerges  out grazing the second surface. The relation between angle of the prism and its critical angle is

  1. $A=C$

  2. $A\neq C$

  3. $A< C$

  4. $A>C$


Correct Option: D

A ray of light is incident at an angle of $60^{\circ}$ on one face of a prism of angle $30^{\circ}$. The emergent ray of right makes an angle of $30^{\circ}$ with incident ray. The angle made by the emergent ray with second face of prism will be

  1. $0^{\circ}$

  2. $90^{\circ}$

  3. $45^{\circ}$

  4. $30^{\circ}$


Correct Option: A

A right-angled prism is set to deviate a ray of light through $90^o$ . If the same prism is to be used for deviating through $180^o$ , the prism must be turned from the previous set position through the angle :

  1. $45^o$

  2. $90^o$

  3. $135^o$

  4. $180^o$


Correct Option: B

Two thin prisms are combined to form an achromatic combination.For prism I, $  A=4^{0}, \mu _{R}=1.35, \mu _{Y}=1.40, \mu _{\nu}=1.42 .  $ For prism II $  \mu _{R}=1.7, \mu _{\gamma}=1.8  $ and $  \mu _{R}=1.9 .  $ Find the prism angle of prism II and the net mean deviation.

  1. $ 0.44^{\circ} $

  2. $ 0.45^{\circ} $

  3. $ 0.48^{\circ} $

  4. $ 0.46^{\circ} $


Correct Option: B

When light rays are incident on a prism at an angle of $45^o$, the minimum deviation is obtained. If the refractive index of the material of the prism is $\sqrt 3$, then the angle of prism will be

  1. $2 \times {\sin ^{ - 1}}\frac{1}{{\sqrt 6 }}$

  2. $45^o$

  3. $60^o$

  4. $90^o$


Correct Option: A

The angle of minimum deviation produced by an equilateral prism is $46^0$. The refractive index of material of the prism.

  1. 1.6

  2. 1.5

  3. 1.4

  4. 1.8


Correct Option: A

The dispersive powers of flint glass and crown glass are $0.053$  and $0.034 $and respectively and their mean refractive indices are $1.68 $ and $1.53$for white light. Calculate the angle of the flint prism required to form an achromatic combination with a crown glass of refracting angle $4^0$

  1. $2^0$

  2. $4^0$

  3. $5^0$

  4. $6^0$


Correct Option: A