Question

Ravi is given lenses with powers
+ 5D, -5D, +10D, -10D and -20 D.
Considering a pair of lenses at a time, which
two lenses will he select to have
combination of total focal length when two
lenses are kept in contact in each case.

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Answer 1

Answer:

-20

Explanation:

total p = p1+p2+p3+p4+p5

Answer 2

Answer:

the correct answer is -10D