Name the lens which can concentrate sun's rays to a point and burn a hole in a piece of paper.

Which of the following can be drawn on a piece of paper ?

Name the objects which can be made with paper.

A child while playing with his father's spectacles, burnt a hole in a piece of tissue paper by focussing the image of the sun on the paper. (a) Name the defect of vision his father is suffering from. (b) List two causes of the defect. ( c) Draw a ray diagram to show this defect may be corrected using a suitable lens.

Name the following : Point at which an incident ray falls .

Name the instrument which can measure accurately the following the thickness of a paper