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A compound microscope is used to enlarge...

A compound microscope is used to enlarge an object kept at a distance 0.03m from its objective which consists of several convex lenses in contact and has focal length 0.02m. If a lens offocal length 0.1m is removed from the objective, find out the distance by which the eyepiece of the microscope must be moved to refocus the image?

A

2.5 cm

B

6 cm

C

15 cm

D

9 cm

Text Solution

Verified by Experts

The correct Answer is:
D
Initially `v_(o) = (u_(o)f_(o))/(u_(o) - f_(o)) = (3xx 2)/(3-2 ) = 6 cm `
Now,
`(1)/(f_(eq)) = (1)/(f_(1)) + (1)/(f_(2)) + (1)/(f_(3)) +…. = (1)/(f_(1)) + (1)/(f._(eq))`
`[ (1)/(f._(eq)) = (1)/(f_(2)) + (1)/(f_(3)) + …. ] `
If one lens is removed then
`(1)/(f_(eq)) = (1)/(f_(eq)) - (1)/(f_(1)) = (1)/(2) - (1)/(10 ) rArr f._(eq) = 2.5 `cm
Finally
`therefore " " v_(o) = (u_(o) f_(eq))/(u_(o) - f_(eq)) = (3 xx 2.5 )/(3 -2.5) = 15` cm
For refocusing the image, eye piece must be moved by
15 − 6 = 9cm .
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