Question

Three lenses \(L_1\), \(L_2\) and \(L_3\), each of focal length \(40\) cm, are placed coaxially. The distance between \(L_1\) and \(L_2\) and between \(L_2\) and \(L_3\) are \(120\) cm and \(20\) cm respectively. An object is kept at a distance of \(80\) cm to the left of lens \(L_1\). Find the distance of the final image formed from the object.

Hint:

If an object is placed at \(2f\) of a convex lens, the image is also formed at \(2f\). If an object is placed at the principal focus of a convex lens, the emerging rays become parallel and the image is formed at infinity.

Answer 1