An extended object of height 2 cm is placed perpendicular to the principal axis at a distance of 60 cm from a convex lens of focal length 20 cm . A plane mirror is placed perpendicular to the principal axis at a distance of 20 cm behind the lens. What are the height and the nature of the final image formed after the second refraction through the lens?

Step-by-step solution

For the first refraction through the convex lens: u = -60 cm , f = +20 cm 1 v₁ - 1 u = 1 f 1 v₁ = 1 20 + 1 -60 = 2 60 v₁ = +30 cm Magnification m₁ = v₁ u = 30 -60 = - 1 2 This image I₁ is formed 30 cm to the right of the lens. Since the plane mirror is at 20 cm , I₁ is 10 cm behind the mirror, acting as a virtual object for it. The plane mirror forms a real image I₂ at 10 cm in front of it (i.e., 10 cm to the right of the lens). Magnification of plane mirror m₂ = +1 . For the second refraction through the lens, lig