ray-optics-and-optical-instruments Question 26
Question: Q. 8. A concave lens of refractive index 1.5 is immersed in a medium of refractive index 1.65 . What is the nature of the lens?
A[Delhi 2015]
Show Answer
Solution:
Ans. The lens behaves as a convex lense.
When the refractive index of a surrounding medium is more than refractive index of material of concave lens than the nature of the lens changes.
Commonly Made Error
- Many candidates wrote the correct lens makers formula but could not relate that $\left(n_{21}-1\right)$ is still positive, so nature of lens will not change.
Answering Tips
- Solve a few problems based on lens maker’s formula and learn what happens when the lens is immersed in (a) rarer medium (b) a denser medium.
