Ray Optics and Optical Instruments · Question 3

The lens combination as shown in the figure, consists of two lenses, L1 and L2, of the focal lengths +10 cm and -10 cm, respectively. The position of the image formed is: [figure]

1. 60 cm to the right of the concave lens
2. 20 cm to the left of the concave lens
3. 60 cm to the left of the concave lens
4. 30 cm to the right of the concave lens

A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is

1. 150
2. 250
3. 100
4. 125

In a certain camera, a combination of four similar thin convex lenses are arranged axially in contact. Then the power of the combination and the total magnification in comparison to the power (p) and magnification (m) for each lens will be, respectively

1. 4p and m4
2. p4 and m4
3. 4p and 4m
4. p4 and 4m

A light ray enters through a right angled prism at point P with the angle of incidence 30 as shown in figure. It travels through the prism parallel to its base BC and emerges along the face AC. The refractive index of the prism is: [figure]

1. 54
2. 52
3. 34
4. 32

A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm. The magnifying power of telescope for viewing a distant object is:

1. 34
2. 28
3. 17
4. 32

Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below :

1. Statement I is correct but statement II is incorrect
2. Statement I is incorrect but Statement II is correct
3. Both Statement I and Statement II are correct
4. Both Statement I and Statement II are incorrect

Light travels a distance x in time t1 in air and 10x in time t2 in another denser medium. What is the critical angle for this medium?

1. -1 ( 10t2t1 )
2. -1 ( t110t2 )
3. -1 ( 10t1t2 )
4. -1 ( t2t1 )

In the figure shown here, what is the equivalent focal length of the combination of lenses (Assume that all layers are thin) ? [figure]

1. -40 cm
2. -100 cm
3. -50 cm
4. 40 cm

Two thin lenses are of same focal lengths (f), but one is convex and the other one is concave. When they are placed in contact with each other, the equivalent focal length of the combination will be :

1. f/4
2. f/2
3. Infinite
4. Zero

A biconvex lens has radii of curvature, 20 cm each. If the refractive index of the material of the lens is 1.5, the power of the lens is

1. +2 D
2. +20 D
3. +5 D
4. Infinity