A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be

A concave mirror gives an image three times as large as the object pla

1.	A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be
Answer» 10 cm 15 cm 20 cm 30 cm Solution :As `m=-(v)/(U)=-3 rArr v=3u=3xx20=60cm` `therefore""(1)/(f)=(1)/(v)+(1)/(u)=(1)/((-60))+(1)/((-20))=-(1)/(15) rArr f=-15cm`

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A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be

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