Physics · PYQ NEET UG 2021
हिन्दीA convex lens 'A' of focal length 20 cm and a concave lens 'B' of focal length 5 cm are kept along the same axis with a distance 'd' between them. If a parallel beam of light falling on 'A' leaves 'B' as a parallel beam, then the distance 'd' in cm will be:
Correct answer · Option 1
15
Explanation
For a parallel beam to remain parallel after passing through the lens combination, the focal points must coincide. Thus, \( d = f_A - f_B = 20 - 5 = 15\text{ cm} \).