A 4.5 cm needle is placed …

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A 4.5 cm needle is placed 12cm away from a convex mirror of focal length 15 cm . give the location of the image and the magnification .describe what happens as the needle is moved farther from the mirror.

Posted by Suruchi Saluja 6 years, 2 months ago

CBSE > Class 10 > Science

1 answers

Prakarsh Paliwal 6 years, 2 months ago

Here, object size , h1 = 4.5 cm object distance, u = –12 cm focal length, f = + 15 cm image distance , v = ? magnification, m = ? As. 1/u + 1/v = 1/f 1/v = 1/f – 1/u Now, putting u = –12 cm and f = +15cm , we get 1/v = 1/15 - 1/-12 = 4+5/60 = 9/60 v = 60/9 = 6.7 cm image is formed 6.7 CM behind the convex mirror. it must be virtual and erect. if h2 is size of image , then m = h2/h1 = -v/u or, m = h2/h1 = –(6.7)/–12 = 0.558 h2 = 0.558 h1 = 0.558 * 4.5 = 2.5 cm As the needle is moved further from the mirror, image moves away from the mirror till it is at focus F of the mirror the size of the image goes on decreasing.

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Posted by Pandey Ji 5 months, 4 weeks ago

CBSE > Class 10 > Science