Ray Optics and Optical Instruments

An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is 25D. Focal length of each of the convex lens is:

1. 50 cm
2. 20 cm
3. 25 cm
4. 500 cm

A light ray is incident on a glass slab of thickness 4 3 cm and refractive index 2. The angle of incidence is equal to the critical angle for the glass slab with air. The lateral displacement of ray after passing through glass slab is cm. (Given 15 = 0.25)

The distance between object and its 3 times magnified virtual image as produced by a convex lens is 20 cm. The focal length of the lens used is cm.

The refractive index of a prism with apex angle A is A/2. The angle of minimum deviation is :

1. m=180 -3A
2. m=180 -4A
3. m=180 -2A
4. m=180 -A

Light from a point source in air falls on a convex curved surface of radius 20 cm and refractive index 1.5. If the source is located at 100 cm from the convex surface, the image will be formed at cm from the object.

The distance between object and its two times magnified real image as produced by a convex lens is 45 cm. The focal length of the lens used is cm.

In an experiment to measure the focal length (f) of a convex lens, the magnitude of object distance (x) and the image distance (y) are measured with reference to the focal point of the lens. The y-x plot is shown in figure. The focal length of the lens is cm. [figure]

A convex mirror of radius of curvature 30 cm forms an image that is half the size of the object. The object distance is :

1. -45 cm
2. -15 cm
3. 45 cm
4. 15 cm

A biconvex lens of refractive index 1.5 has a focal length of 20 cm in air. Its focal length when immersed in a liquid of refractive index 1.6 will be:

1. -16 cm
2. +16 cm
3. +160 cm
4. -160 cm

If the distance between object and its two times magnified virtual image produced by a curved mirror is 15 cm, the focal length of the mirror must be:

1. -10 cm
2. -12 cm
3. 15 cm
4. 10/3 cm