1.

An object is kept in front of a concave mirror of focal length 15 cm. The image formed is three times the size of the object. Calculate the two possible distances of the object from the mirror.

Answer» `{:(f=-15 cm),(m=-3):}`
`m=(-v)/(u)=-3`
`rArr" "v=3u`
Mirror equation
`(1)/(f)=(1)/(v)+(1)/(u)`
`(1)/(-15)=(1)/(3u)+(1)/(u)`
`(1)/(-15)=(1+3)/(3u)=(4)/(3u)`
`u=(4xx(-15))/(3)=-20 cm`
`u=-20cm`


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