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QJEEM07Pha5b7: JEE Main 2007 Physics - Class 12 JEEM07Pha5b7 Solution: Two lenses of power and are in contact with each other. The…

Two lenses of power

-15

D

and

+5

D

are in contact with each other. The focal length of the combination is

Step-by-Step Verified Solution

Power of combination is given by

P = {P_1} + {P_2} = \left( { - 15 + 5} \right)D

\,\,\,\,\,\,\,\,\, = - 10D.

Now,

P = {1 \over f} \Rightarrow f = {1 \over P} = {1 \over { - 10}}

metre

\therefore

f = - \left( {{1 \over {10}} \times 100} \right)cm = - 10\,cm.