Question

A student places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the umage of the flame on a screen. After that he gradually moves the flame towards the lens and each time focuses the image on the screen.
(a) In which direction-toward or away from the lens, does he move the screen to focus the image ?
(b) How does the size of the image change ?
(c) How does the intensity of the image change as the flame moves towards the lens ?
(d) Approximately for what distance between the flame and the lens, the image formed on the screen is inverted and of the same size ?

Answer 1

(a) He will move the screen away from the lens to focus the image.
(b) Size of the image goes on increasing.
(c) Intensity of image goes on decreasing.
(d) About 20 cms.