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A `5 cm` long needle is placed `10 cm` from a convex mirror of focul length `40 cm`. Find the position, nature and size of image of the needle. What happens to the size of image when needle is moved farhter away from the mirror ? |
Answer» Here, `h_(1) = 5 cm, u = -10 cm`, `f = 40 cm` From `(1)/(v) = (1)/(f) - (1)/(u) = (1)/(40) - (1)/(-10) = (5)/(40) = (1)/(8)` `v = 8 cm` Image is virtual, erect and is formed `8 cm` behind the mirror. Magnification, `m = (h_(1))/(h_(2)) = (-v)/(u) = (-8)/(-10) = (4)/(5)` `h_(2) = (4)/(5)h_(1) = (4)/(5) xx 5 = 4 cm` As needle is moved farther away from the mirror, image shifts towards the focus and its size goes on decreasing. |
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