Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of $15 \mathrm{cm}$ from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?

Draw ray diagrams showing the image formation by a concave mirror when an object is placed

(a) between pole and focus of the mirror

(b) between focus and centre of curvature of the mirror

(c) at centre of curvature of the mirror

(d) a little beyond of curvature of the mirror

(e) at infinity

Draw ray diagrams showing the image formation by a convex lens when an object  is placed

(a) between optical centre and focus of the lens

(b) between focus and twice the focal length of the lens

(c) at twice the focal length of the lens

(d) at infinity

(e) at the focus of the lens

Draw ray diagrams showing the image formation by a concave lens when an object is placed.

(a) at the focus of the lens

(b) between focus and twice the focal length of the lens

(c) beyond twice the focal length of the lens.

Draw ray diagrams showing the image formation by a convex mirror when an object is placed.

(a) at infinity

(b) at finite distance from the mirror.