a convex lens placed at a distance of 0.1m from an object produces a magnified image on the screen without disturbing the object or the screen, the lens is moved by 0.2m towards the screen and a diminished image is formed on screen. The focal length of lens in cm must be?
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Answer:
The focal length is 7.5 cm
Explanation:
According to the problem the distance between the lens and the object is 0.1m
The distance of the image is (0.2+0.1)= 0.3
As we know the relation between the focal length
1/f= 1/v - 1/u [ where v is the image distance and u is the object distance]
= 1/0.3 - 1/(-0.1)
= 4/0.3
Therefore f = 0.3/4
= 0.075 m= 7.5 cm
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