A lens forms an upright and diminished image of an object placed at its focal point. Name the lens and draw a ray diagram to show the formation of an image.

State the changes in the position, size and nature of the image when the object is brought from infinity up to the convex lens. Illustrate your answer by drawing the ray diagrams.

Draw a ray diagram to show how a converging lens can form a real and enlarged image of an object.

Draw a ray diagram to show how a converging lens can form an image of the Sun. Hence give a reason for the term 'burning glass' for a converging lens used in this manner.