Ray Optics and Optical Instruments

A bi-convex lens has radius of curvature of both the surfaces same as 1/6 cm. If this lens is required to be replaced by another convex lens having different radii of curvature on both sides (R1 R2), without any change in lens power then possible combination of R1 and R2 is :

1. 13 cm and 17 cm
2. 15 cm and 17 cm
3. 13 cm and 13 cm
4. 16 cm and 19 cm

A ray of light suffers minimum deviation when incident on a prism having angle of the prism equal to 60 . The refractive index of the prism material is 2. The angle of incidence (in degrees) is

Let u and v be the distances of the object and the image from a lens of focal length f. The correct graphical representation of u and v for a convex lens when |u| > f, is

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Two light beams fall on a transparent material block at point 1 and 2 with angle 1 and 2, respectively, as shown in figure. After refraction, the beams intersect at point 3 which is exactly on the interface at other end of the block. Given : the distance between 1 and 2, d = 4 3 cm and 1 = 2 = -1 ( n22n1 ), where refractive index of the block n2 > refractive index of the outside medium n1, then the thickness of the block is cm. [figure]

At the interface between two materials having refractive indices n1 and n2, the critical angle for reflection of an em wave is 1C. The n2 material is replaced by another material having refractive index n3 such that the critical angle at the interface between n1 and n3 materials is 2C. If n3 > n2 > n1; n2n3 = 25 and 2C - 1C = 12, then 1C is :

1. -1 ( 16n1 )
2. -1 ( 13n1 )
3. -1 ( 56n1 )
4. -1 ( 23n1 )

A convex lens made of glass (refractive index = 1.5) has focal length 24 cm in air. When it is totally immersed in water (refractive index = 1.33), its focal length changes to

1. 96 cm
2. 72 cm
3. 24 cm
4. 48 cm

Two concave refracting surfaces of equal radii of curvature and refractive index 1.5 face each other in air as shown in figure. A point object O is placed midway, between P and B. The separation between the images of O, formed by each refracting surface is : [figure]

1. 0.124R
2. 0.114R
3. 0.411R
4. 0.214R

Two identical symmetric double convex lenses of focal length f are cut into two equal parts L1, L2 by AB plane and L3, L4 by XY plane as shown in figure respectively. The ratio of focal lengths of lenses L1 and L3 is [figure]

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

A thin prism P1 with angle 4 made of glass having refractive index 1.54, is combined with another thin prism P2 made of glass having refractive index 1.72 to get dispersion without deviation. The angle of the prism P2 in degrees is

1. 1.5
2. 16/3
3. 3
4. 4

A hemispherical vessel is completely filled with a liquid of refractive index . A small coin is kept at the lowest point (O) of the vessel as shown in figure. The minimum value of the refractive index of the liquid so that a person can see the coin from point E (at the level of the vessel) is . [figure]

1. 32
2. 32
3. 3
4. 2