A) act as a convex lens only for the objects that lie on its curved side.
B) act as a concave lens for the objects that lie on its curved side.
C) act as a convex lens irrespective of the side on which the object lies.
D) act as a concave lens irrespective of side on which the object lies.
Correct Answer: C
Solution :
| Option [c] is correct. |
| Explanation: As we know the relations between f, µ,\[{{R}_{1}}\] and \[{{R}_{2}}\] is known as lens maker's formula: |
| \[\frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] |
| \[{{R}_{1}}=\infty ,{{R}_{2}}=-R\] |
| \[f=\frac{R}{(\mu -1)}\] |
| Given that, |
| \[R=20cm,\] |
| \[\mu =1.5\] |
| Put the values; |
| \[f=\frac{R}{\mu -1}=\frac{20}{15-1}=40\operatorname{cm}\] |
| As \[f>0,\] it means converging nature of the lens. |
| So, lens act as a convex lens irrespective of the side on which the object lies. |
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