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(Ăźi) A 10 mm long pin is placed vertically in frontof a concave mirror. A 5 mm long image of thepin is formed at 30 cm in front of the mirror,find the focal length of this mirror[Ans.ăŤ-10 cm] |
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Answer» We know that m= h'/h= -v/u 5/10=-30/u u=-300/5 u=-60cm 1/f=1/v+1/u 1/f = 1/-30 + 1/-60 1/f = -2-1/60 1/f=-3/60 1/f=-1/20 f=-20cm Therefore the focal length of the concave mirror is 20 cm front of the mirror |
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