JEE PYQ: Ray Optics Question 35
Question 35 - 2019 (08 Apr Shift 2)
A convex lens (of focal length 20 cm) and a concave mirror, having their principal axes along the same lines, are kept 80 cm apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of 30 cm to the left of the convex lens, its image remains at the same position even if the concave mirror is removed. The maximum distance of the object for which this concave mirror, by itself would produce a virtual image would be:
(1) 30 cm
(2) 25 cm
(3) 10 cm
(4) 20 cm
Show Answer
Answer: (1)
Solution
For lens: $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$ or $\frac{1}{v} + \frac{1}{30} = \frac{1}{20}$ $\therefore v = +60$ cm According to the condition, image formed by lens should be the centre of curvature of the mirror, and so $2f’ = 20$ or $f’ = 10$ cm
BETA
