A)The magnifying power of a simple microscope is 6. The focal length of its lens in meters will be ? (Least distance of distinct visionis 25cm)
A. 0.05
B.0.06
C.0.25
D.0.12
B) the focal length of one lens is -40 cm and that if the other is +20 cm . The foxal length of this combination wil be
A.15.2cm
B.40cm
C.-40cm
D.35cm
A. 0.05
B.0.06
C.0.25
D.0.12
B) the focal length of one lens is -40 cm and that if the other is +20 cm . The foxal length of this combination wil be
A.15.2cm
B.40cm
C.-40cm
D.35cm
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Answer:
A) Option A 0.05
B) Option B 40 cm
Explanation:
(A) Magnification of the lens
Least distance of Distinct vision
We know that if focal length of the lens is f then
or,
m
(B) Given two focal lengths
Power of the lens is reciprocal of the focal length
Power of the lenses will be
Combined power of the lens
Therefore, the combined focal length will be
Hope this helps.