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Question:

In a compound microscope the focal length of objective lens is 1.2 cm and focal length of eye piece is 3.0 cm. When object is kept at 1.25 cm in from of objective, final image is formed at infinity. Magnifying power of the compound microscope should be:

150

100

400

200

Solution:

Given
fe=3cm and fo=1.2cm
uo=1.25cm
ve=∞
From , 1/uo + 1/vo = 1/fo, we get
1/vo = 1/1.2 - 1/1.25
vo=30cm
Magnification of microscope
m = vo/uo (D/fe)
m = 30/1.25 (25/3) = 200.