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A telescope has an objective lens of foc...

A telescope has an objective lens of focal length 200 cm and an eye piece with focal length 2 cm. If this telescope is used to see a 50 m tall building at a distance of 2 km, what is the height of the image of the building formed by the objective lens?

A

5 cm

B

10 cm

C

1 cm

D

2 cm

Text Solution

Verified by Experts

The correct Answer is:
A
From the formula for convex lens,
`(1)/(v)-(1)/(u)=(1)/(f)`
`therefore" "v=(fxxu)/(u-f)=(200xx200xx10^(3))/([200xx10^(3)-200])=(200xx10^(3))/(999)`
Also, magnification,
`m=|(v)/(u)|=|(t)/(O)|`
`=(200xx10^(3))/(999xx200xx10^(3))=(I)/(50xx100)`
`I=(5000)/(999) cong 5 cm`.
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