An object is placed on the principal axis of convex lens of focal length 10 cm as shown. A plane mirror is placed on the other side of lens at a distance of 20 cm. The image produced by the plane mirror is 5 cm inside the mirror. The distance of the object from the lens i $s ____$ cm.

Question

G1 Physics · Accepted Answer

The mirror image is 5 cm behind the mirror, so the lens forms an intermediate image 5 cm in front of the mirror, i.e. 15 cm from the lens. Using the lens formula 1/v - 1/u = 1/f with v = 15 cm and f = 10 cm: 1/15 - 1/u = 1/10, giving u = -30 cm. Hence the object distance is 30 cm.

An object is placed on the principal axis of convex lens of focal length 10 cm as shown. A plane mirror is placed on the other side of lens at a distance of 20 cm. The image produced by the plane mirror is 5 cm inside the mirror. The distance of the object from the lens i s ____ cm.