A convex lens of focal length 20 cm is placed in front of a convex mirror with principal axis coinciding each other. The distance between the lens and mirror is 10 cm. A point object is placed on principal axis at a distance of 60 cm from the convex lens. The image formed by combination coincides the object itself. The focal length of the convex mirror is ______ cm.
← JEE Main 2022 · 25 Jul · Shift 2
PhysicsInteger+4 / -1Question 59 of 90
JEE Main 2022 · 25 Jul · Shift 2, Physics question 59
Answer and worked solution
Official answer: 10
Lens image of the object at 60 cm is at 30 cm, i.e. 20 cm behind the mirror. For rays to retrace, this point is the mirror's centre of curvature: cm, cm.
Answer: 10