What are primary focus and secondary focus of convex lens?

Principal focus of convex lens:

Principal focus of convex lens:

Principal focus of concave lens:

Principal focus of concave lens:

When a object is placed in between principal focus and optical centre of convex lens, a _______ is formed .

Calculate the position of the image of an object when placed at (a) focus of a convex lens. (b) focus of a convex lens.

a) With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principle axis, optical center, principal focus and focal length of the convex lens on the diagram. b) State whether convex lens has a real focus or a virtual focus. c) List some things that convex lens and concave mirror have in common.

Calculate the position of the image of an object when placed at (a) focus of a convex lens. (b) focus of a concave lens.

Use the thin lens formula to show that an object placed within the focus of a convex lens produces a virtual and enlarged image.