The focal length of a combination of lenses formed with lenses having – McqOptions

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1.	The focal length of a combination of lenses formed with lenses having powers of + 2.50 D and - 3.75 D will be [RPMT 1997]
A.	- 20 cm
B.	- 40 cm
C.	- 60 cm
D.	- 80 cm
Answer» E.

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