We wish to obtain an equal-sized inverted image of a candle flame on a screen kept at a distance of 4 m from the candle flame.
(a) Name the type of lens that should be used.
(b) What should be the focal length of the lens and at what distance from the candle flame the lens be placed?
(c) Draw a labeled diagram to show the image formation in this case.
(a) Convex Lens
(b) Distance of Flame from lens = 4m = 4
For equal sized inverted image u = 2f = 4
f is the focal length of lens
So, Focal length of lens is 2m.
(c) Ray Diagram
Distance between the candle flame and the screen is 4m.
Hence the distance between the lens and the candle flame is 2m so as to get real inverted and same size image.
So the focal length is 1 m.