Ray Optics and Optical Instruments · Question 35

A concave-convex lens of refractive index 1.5 and the radii of curvature of its surfaces are 30 cm and 20 cm, respectively. The concave surface is upwards and is filled with a liquid of refractive index 1.3. The focal length of the liquid-glass combination will be

1. 70011 cm
2. 60011 cm
3. 80011 cm
4. 50011 cm

Two thin convex lenses of focal lengths 30 cm and 10 cm are placed coaxially, 10 cm apart. The power of this combination is:

1. 5 D
2. 1 D
3. 20 D
4. 10 D

A lens having refractive index 1.6 has focal length of 12 cm, when it is in air. Find the focal length of the lens when it is placed in water. (Take refractive index of water as 1.28)

1. 355 mm
2. 655 mm
3. 288 mm
4. 555 mm

A container contains a liquid with refractive index of 1.2 up to a height of 60 cm and another liquid having refractive index 1.6 is added to height H above first liquid. If viewed from above, the apparent shift in the position of bottom of container is 40 cm. The value of H is cm. (Consider liquids are immiscible)

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below:

1. Both (A) and (R) are correct and (R) is the correct explanation of (A)
2. (A) is correct but (R) is not correct
3. (A) is not correct but (R) is correct
4. Both (A) and (R) are correct but (R) is not the correct explanation of (A)

A mirror is used to produce an image with magnification of 14. If the distance between object and its image is 40 cm, then the focal length of the mirror is .

1. 10 cm
2. 12.7 cm
3. 10.7 cm
4. 15 cm

A transparent block A having refractive index = 1.25 is surrounded by another medium of refractive index = 1.0 as shown in the figure. A light ray is incident on the flat face of the block with incident angle as shown in the figure. What is the maximum value of for which light suffers total internal reflection at the top surface of the block? [figure]

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

When an object is placed 40 cm away from a spherical mirror an image of magnification 12 is produced. To obtain an image with magnification of 13, the object is to be moved :

1. 20 cm away from the mirror.
2. 20 cm towards the mirror.
3. 80 cm away from the mirror.
4. 40 cm away from the mirror.

Distance between object and its image (magnified by - 13) is 30 cm. The focal length of the mirror used is ( x4 )cm, where magnitude of value of x is .

A finite size object is placed normal to the principal axis at a distance of 30 cm from a convex mirror of focal length 30 cm. A plane mirror is now placed in such a way that the image produced by both the mirrors coincide with each other. The distance between the two mirrors is :

1. 45 cm
2. 15 cm
3. 22.5 cm
4. 7.5 cm