CBSE Class 10 Science 2017 Delhi Term II Set 1 Paper

Question : 36

Total: 36

A student places a candle flame at a distance of about 60‌cm from a convex lens of focal length 10‌cm and focuses the image 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?

Solution:

(a) He should move the screen away from the convex lens to focus the image.
(b) The size of the image increases.
(c) The intensity of the image decreases as the flame moves towards the lens.
(d) The flame should be placed at a distance of 20‌cm from the convex lens. (i.e., at radius of curvature, R=2f )

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