Search any question & find its solution
Question:
Answered & Verified by Expert
Two thin lenses of focal lengths $f_1$ and $f_2$ are in contact and coaxial. The power of the combination is
Options:
Solution:
2004 Upvotes
Verified Answer
The correct answer is:
$\frac{f_1+f_2}{f_1 f_2}$
If two thin lenses of focal lengths $f_1, f_2$ are placed in contact coaxially, then equivalent focal length of combination is
$$
\frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}-\frac{0}{f_1 f_2}=\frac{1}{f_1}+\frac{1}{f_2}
$$
Power for the combination is
$$
P=\frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}=\frac{f_1+f_2}{f_1 f_2}
$$
$$
\frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}-\frac{0}{f_1 f_2}=\frac{1}{f_1}+\frac{1}{f_2}
$$
Power for the combination is
$$
P=\frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}=\frac{f_1+f_2}{f_1 f_2}
$$
Looking for more such questions to practice?
Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.