1. Tardigrade
  2. Question
  3. Physics
  4. A combination of convex and concave lenses has power 4 D. If the convex lens has power 5 D, the focal length of the concave lens will be

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A combination of convex and concave lenses has power $4\, D$. If the convex lens has power $5\, D$, the focal length of the concave lens will be

Uttarkhand PMTUttarkhand PMT 2010

Solution:

Power of combination
$P=P_{1}+P_{2} $
$\Rightarrow 4=5+P_{2} $
$\Rightarrow P_{2}=4-5=-1 D $
$\therefore -1=P_{2}=\frac{100}{f( cm )} $
$\Rightarrow f=-100 \,cm$