Optics Question 129
Question: A compound microscope is used to enlarge an object kept at a distance 0.03m from it’s objective which consists of several convex lenses in contact and has focal length 0.02m. If a lens of focal length 0.1m is removed from the objective, then by what distance the eye-piece of the microscope must be moved to refocus the image
Options:
A) 2.5 cm
B) 6 cm
C) 15 cm
D) 9 cm
Show Answer
Answer:
Correct Answer: D
Solution:
If initially the objective (focal length Fo) forms the image at distance vo then
Now as in case of lenses in contact
So if one of the lens is removed, the focal length of the remaining lens system
Therefore
This lens will form the image of same object at a distance
So to refocus the image, eye-piece must be moved by the same distance through which the image formed by the objective has shifted i.e. 15 ? 6 = 9 cm.
