1.

A point object is placed at a distance of 20 cm from a thin plano-concex lens of focal length 15 cm. The plane surface of the lens is now silvered. The image created by the is at :

Answer»

`60 CM` to the left of the system.
`60 cm` to the right of the system.
`12 cm` to the left of the system.
`12 cm` to the right of the system.

Solution :By mirror-lens combination formula
`(1)/(F)=(1)/(f_(m))-(1)/(f_(L))`
`(1)/(F)=(1)/(infty)-(2)/(15)`
By mirror formula
`(1)/(F)=(1)/(u)+(1)/(v) RARR -(2)/(15)=(1)/(-20)+(1)/(v)`
`rArr (1)/(v)=(1)/(20)-(2)/(15)=(3-8)/(60)`
`v=-12 cm` negartive means TOWARD left


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