Question

16. Find the focal length of a convex lens is 10cm. A candle of height 12cm is placed at a distance
or 20can from that lens. The position nature and length of image of candle.
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Answer 1

Explanation:

Height of the object =2 cm

U(object distance) = -15 as u is always negative

F = -10 (as it is always negative for concave miror and lens )

1/F =1/v + 1/u

-1/10 = 1/v + (-1/15)

-1/10 +1/15 =v

-3+2/30 =v

V=-30cm

Hi/Ho = - V/U

Hi /2 = -(-30/15)

Hi =-30×2÷15

Hi =-4cm (Real and inverted)