An object 2 cm high is placed at a distance of 16 cm from a concave mirror, which produces a real image 3 cm high. What is the focal length of the mirror ?
A
-9.6 cm
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B
-3.6 cm
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C
-6.3 cm
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D
-8.3 cm
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Solution
The correct option is A -9.6 cm Here h1 = 2 cm, u = -16 cm, h2 = -3 cm (Since image is real and inverted.) ∵m=h2h1=−vu∴v=−h2h1u=32×(−16)=−24cm 1f=1v+1u=−124−116=−2−348=−548;f=−485=−9.6cm