A real image can be obtained on a screen while a virtual image cannot. Explain why?

State the position, nature and size of the image  formed by a convex lens of focal length $0.3 \mathrm{m}$ for the following positions of the project

(i) $0.2 \mathrm{m}$  (ii) $0.4 \mathrm{m}$   (iii) $0.8 \mathrm{m}$

Which of the above cases represents the use of convex lenses in a magnifying glass, in a camera and in a film projector ?

An object of height $4 \mathrm{cm}$ placed $10 \mathrm{cm}$ away from a thin lens of focal length $20 \mathrm{cm}$ gives a virtual image.

(I) if the lens is convex, find the position and size of image formed. Also draw a labelled ray diagram to show the formation of image.

An object of height $4 \mathrm{cm}$ placed $10 \mathrm{cm}$ away from a thin lens of focal length $20 \mathrm{cm}$ gives a virtual image.

If the lens is concave, find the position and size of the image formed.