Ray Optics and Optical Instruments

A thin plano convex lens made of glass of refractive index 1.5 is immersed in a liquid of refractive index 1.2. When the plane side of the lens is silver coated for complete reflection, the lens immersed in the liquid behaves like a concave mirror of focal length 0.2 m. The radius of curvature of the curved surface of the lens is

1. 0.15 m
2. 0.10 m
3. 0.25 m
4. 0.20 m

A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of f1 in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of f2 when it is immersed in a liquid of refractive index 1.2. If both the lenses are made of same glass of refractive index 1.5, the ratio of f1 and f2 will be

1. 2:3
2. 1:3
3. 1:2
4. 3:5

A photograph of a landscape is captured by a drone camera at a height of 18 km. The size of the camera film is 2 cm 2 cm and the area of the landscape photographed is 400 km2. The focal length of the lens in the drone camera is :

1. 2.8 cm
2. 0.9 cm
3. 2.5 cm
4. 1.8 cm

What is the lateral shift of a ray refracted through a parallel-sided glass slab of thickness ' h ' in terms of the angle of incidence ' i ' and angle of refraction ' r ', if the glass slab is placed in air medium?

1. h
2. h (i-r) r
3. h (i-r) r
4. h (i-r) r

A spherical surface of radius of curvature R, separates air from glass (refractive index =1.5). The centre of curvature is in the glass medium. A point object 'O' placed in air on the optic axis of the surface, so that its real image is formed at 'I' inside glass. The line OI intersects the spherical surface at P and PO=PI. The distance PO equals to

1. 5R
2. 2R
3. 1.5R
4. 3R

Given a thin convex lens (refractive index 2), kept in a liquid (refractive index 1, 1< 2) having radii of curvatures |R1| and |R2|. Its second surface is silver polished. Where should an object be placed on the optic axis so that a real and inverted image is formed at the same place?

1. ( 2+ 1)|R1|( 2- 1)
2. 1|R1| |R2| 2 (2|R1|+|R2| )- 1 |R1| |R2|
3. 1|R1| |R2| 2 (|R1|+|R2| )- 1|R1|
4. 1|R1| |R2| 2 (|R1|+|R2| )- 1|R2|

A concave mirror of focal length f in air is dipped in a liquid of refractive index . Its focal length in the liquid will be:

1. f
2. f
3. f
4. f( -1)

The refractive index of the material of a glass prism is 3. The angle of minimum deviation is equal to the angle of the prism. What is the angle of the prism?

1. 60
2. 50
3. 58
4. 48

In the diagram given below, there are three lenses formed. Considering negligible thickness of each of them as compared to |R1| and |R2|, i.e., the radii of curvature for upper and lower surfaces of the glass lens, the power of the combination is [figure]

1. - 16 ( 1|R1|- 1|R2| )
2. - 16 ( 1|R1|+ 1|R2| )
3. 16 ( 1|R1|+ 1|R2| )
4. 16 ( 1|R1|- 1|R2| )

Given is a thin convex lens of glass (refractive index ) and each side having radius of curvature R. One side is polished for complete reflection. At what distance from the lens, an object be placed on the optic axis so that the image gets formed on the object itself?

1. R/
2. R/(2 -1)
3. R/(2 -3)