Question
Sat March 12, 2011 By: Renuka Sahu

two lenses have focal lengths +10 cm and -15 cm . they are kept in contact . what is the focal lenth of combined lens ? what is the nature of the lens and also find the power of the combined lens.

Expert Reply
Sat March 12, 2011
Dear student
Combined focal length, F = (10)(-15)/ (10 -15) = -150/-5 = 30 cm
nature of lens = convex.
Power of combined lens, P = 1/F (in m) = 100/30 = 33.3 D
Hope this clarifies your doubt.
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Team
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