A bi-convex lens of focal length 20 cm is placed at a distance l = 6 cm from a plane mirror. If the medium between mirror and lens is water, find the equivalent focal length of the system. A bi-convex lens of focal length 20 cm is placed at a distance l = 6 cm from a plane mirror. If the medium between mirror and lens is water find the equivalent focal length of the system. September 9, 2020 Category: Uncategorised (JEE Advanced Physics by BM Sharma + GMP Solutions) , Facebook Messenger WhatsApp Share this:TwitterFacebook Related