Geometrical optics

A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that the end closer to the pole is 20 cm away from it. Find the length of the image.

• 10 cm

• 15 cm

• 20 cm

• 5 cm

An object P is placed 21 cm in front of a concave mirror

of radius of curvature 20 cm. A glass slab of thickness 3 cm and refractive index 1.5 is placed close to the mirror in the space between the object and the mirror. Find the position of the final image formed. The distance of the nearer surface of the slab from the mirror is 10 cm.

• on object P itself

• 5 cm to the left of P

• 5 cm to the right of P

• None of the above

Locate the image formed by refraction in the situation shown in figure. The point C is the centre of curvature.

• 75 cm to the right of O

• 75 cm to the left of O

• 25 cm to the left of O

• 100 cm to the right of O

A illuminating light source is placed 16 cm below the surface of water. Find the radius of circle of illuminance.

• 64/3 cm

• 16/3 cm

• 12 cm

• 8 cm

A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut- lens will be

• 2 D

• 3 D

• 4 D

• 5 D

A point source S is placed midway between two concave mirrors facing each other and separated by a distance “d”. Each of the mirrors have flack length equal to f. What should be value of “ d ” such that only one image is formed.

• f or 2f

• 2f or 4f

• 3f or 6f

• f or 3f

A light ray, going through a prism with the angle of prism 60°, is found to deviate by 30°. What should be the maximum value if refractive index of prism material

• 1.41

• 1.51

• 1.61

• 1.73

The minimum deviations suffered by red, yellow and violet beams passing through an equilateral transparent prism are 38.4°, 38.7° and 39.2° respectively. Calculate the dispersive power of the medium.

• 0.106

• 0.206

• 0.306

• 0.0206

A flint glass prism and a crown glass prism are to be combined in such a way that the deviation of the mean ray is zero. The refractive index of flint and crown glasses for the mean ray are 1.620 and 1.518 respectively. If the refracting angle of the flint prism is 6.0°, what would be the refracting angle of the crown prism ?

• 6.8^o

• 7.2^o

• 4.6^o

• 3.8^o

A convex lens produces a double size real image when an object is placed at a distance of 18 cm from it. Where should the object be placed to produce a triple size real image ?

• 12 cm

• 20 cm

• 16 cm

• 24 cm