A parallel beam of rays is incident on a convergent lens with a focal length of `40 cm.` Where a divergent lens with a focal length of `15 cm` be placed for the beam of rays to remain parallel after passing through the two lenses.

A parallel beam of rays is incident on a convergent lens with a focal length of 40 cm. Where should a divergent lens with a focal length of 15 cm be placed for the beam of rays to remain parallel after passing through the two lenses.

A source of light is located at double focal length from a convergent lens. The focal length of the lens is f=30cm. At what distance from the lens should a flat mirror be placed, so that the rays reflected from the mirror are parallel after passing through the lens for the second time?

A source of light is located at double focal length from a convergent lens. The focal length of the lens is f=30cm. At what distance from the lens should a flat mirror be placed, so that the rays reflected from the mirror are parallel after passing through the lens for the second time?

A converging lens of focal length 40 cm is kept in contact with a diverging lens of focal length 30 cm. Find the focal length of the combination.

A converging lens L_(1) of focal length 20 cm is separated by 8 cm from a diverging lens L_(2) of focal length 30cm. A parallel beam of light falls on L_(1) after passing through L_(2) is focussed at point P. Calculate V.

A converging beam of light is incident on a concave lens of focal length 20 cm. In the absence of the lens, the beam converges at a point 10 m behind the lens. Find where the beam will converge/diverge after refraction.

A converging beam of light is incident on a concave lens of focal length 20 cm. In the absence of the lens, the beam converges at a point 10 m behind the lens. Find where the beam will converge/diverge after refraction.

A convex lens of focal length 100 cm and a concave lens of focal length 10 cm are placed coaxialiy at a separation of 90 cm. If a parallel beam of light is incident on convex lens, then after passing through the two lenses the beam