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Q.
Focal length of a convex lens will be maximum for
BVP MedicalBVP Medical 2011
Solution:
From lens makers formula $ \frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right) $ $ f\propto \frac{1}{(\mu -1)} $ $ f\propto \frac{1}{\mu } $ $ \Rightarrow $ $ \mu \propto \frac{1}{\lambda } $ So, $ f\propto \lambda $ But wavelength of red light is more as compared to other given light. Hence, focal length of convex lans is maximum for red light.