HARD

12th West Bengal Board

IMPORTANT

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A right-angled prism is kept immersed in water. When a ray of light is allowed to be incident on one of the faces of the prism adjoining the right angle normal to the face, the ray is found to be totally reflected by the face opposite to the right angle and to emerge through the other face adjoining the right angle. But when the ray of light is allowed to be normally incident on the other face adjoining the right angle, it emerges through the face opposite to the right angle and there is total internal reflection.

If the other two angles of the prism be $60 °$ and $30 °$ , what information can you gather about the refractive index of the material of the prism? Given RI of water with respect to vacuum $= 1.33$ and $V_{3} = 1.732 .$

Important Questions on Refraction of Light

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 29

Three right angled prisms of refractive indices

μ_{1}, μ_{2} . μ_{3}

are fitted together so that the faces of the middle prism are in contact with one of the outside prisms, Fig.

13.76

Question Image

If a ray passes through the composite block without any deviation, show that $μ_{1} {}^{2}+ μ_{2}^{2} + μ_{3} {}^{2}= 1 .$

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 30

The refractive index of the material of a prism of refracting angle

45 °

1.6

for a certain monochromatic ray. What would be the minimum angle of incidence of this ray on the prism so that no total internal reflection takes place as the ray comes out of the prism ?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 31

A ray of light incident normally on one face of a right angled isosceles prism is found to be totally reflected Fig. $13.77$ . What is the minimum value of the refractive index of the material of the prism? When the prism is immersed in water, trace the path of the emergent ray for the same incident ray, indicating values of all the angles. $(μ_{w} = \frac{4}{3})$ .

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HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 32

A point source of light

S

is placed at the bottom of a vessel containing a liquid of refractive index

\frac{5}{3}

. A person is viewing the source from above the surface. There is an opaque disc of radius

1 cm

flowing on the surface. The centre of the disc lies vertically above the source

S

. The liquid from the vessel is gradually drained out through a tap. What is the maximum height of the liquid for which the source cannot at all be seen from above ?

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 33

A vertical microscope is focussed on a point at the bottom of an empty tank. Water (refractive index

\frac{4}{3}

) is then poured into the tank. The height of the water column is

4 cm

. Another lighter liquid which does not mix with water and which has refractive index of

\frac{3}{2}

is then poured over the water. The height of the liquid is

2 cm

. What is the vertical distance through which the microscope must be moved to bring the object in focus again ?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 34

A concave mirror of small aperture and of focal length

8 cm

lies on a bench with its face upward and a pin is moved up and down along the axis of the mirror. If the mirror be filled with a thin layer of water of refractive index

\frac{4}{3}

, find at what point the image of the pin will coincide with itself.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 1

If the speed of light in medium no.

1

and medium no.

2

v_{1}

and

v_{2}

respectively, then the r.i. of medium no.

2

with respect to medium no.

1

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 2

If the speed of light in two media of r.i.

μ_{1}

and

μ_{2}

v_{1}

and

v_{2}

respectively, then

Important Questions on Refraction of Light

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