1.

An object is placed in front of a concave mirror of focal length 20 cm. The image formed is three times the size of the object. Calculate two possible distances of the object from the mirror?

Answer»

SOLUTION :`m= pm 3`
`m=(-v)/u=+3` for virtual image
`v=-3u`
`1/v+1/u=1/f`
`1/(-34)+1/u=-1/20`
`u=-40/3 CM`
`m=(-v)/u=-3` for real image
`v=3u`
`1/v+1/u=1/f`
`1/(3u)+1/u=-1/ 20`
`u=-80 /3CM`


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