Question 4(ii)
(a) Figs. I and II show the incident and transmitted rays through lens kept in a box in each case. Draw the lens and complete the path of rays through it.
(b) What is the difference between double convex and bi-convex lens?
(c) Does convex lens always form real images?
(a) In Fig I, the rays are diverging, hence a concave lens is placed inside the box:
In Fig II, the rays are converging, hence a convex lens is placed inside the box:
(b) In case of double convex lens the two surfaces may have any values for the two radii of curvature of the two surfaces while in bi-convex lens the radii of curvature of the two surfaces, have the same value. So, all double convex lenses may not be bi-convex but every bi-convex lens is a double convex lens.
(c) No, when the distance of the object from the lens is less than the focal length of the lens, then convex lens will form virtual image.