In Fig. a convex, lens L is placed at a distance of 36 cm from a screen. If a point-source P is placed at 56 cm from the screen then a circular spot of light of diameter equal to the diameter of the lens is formed. Show the image formation by a ray diagram. Calculate upto what distance the source be displaced so that its clear image can be formed on the screen.

A convex lens is placed at a distance of 40 cm from a screen. A point source is placed at a distance of 60 cm from the screen on the same side of the lens. At this position of point-source, a circular spot of light of diameter equal to the lens is formed. Show the formation of image by a ray diagram. Up to what distance the source be displaced so that its clear image can be formed on the screen?

A convex lens of focal length 20 cm is placed at a distance of 30 cm from a screen. Where should an object be placed so as to form its real image on the screen?

A convex lens of power 4D is placed at a distance of 40 cm from a wall at what distance from the lens should a candle be placed so that its image is formed on the wall?

A convex lens of power 4 D is placed at a distance of 40 cm from a wall . At what distance from the lens should a candle be placed so that its image is formed on the wall ?

A converging lens of focal length 5 cm is placed at a distance of 20 cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?

When an object is placed at a distance of 15 cm from a convex lens, a real image is formed at a distance of 30 cm. What is the focal length of the lens?