Question

Assertion : A convex lens of glass $(\mu = 1.5)$ behave as a diverging lens when immersed in carbon disulphide of higher refractive index $(\mu = 1.65)$.
Reason: A diverging lens is thinner in the middle and thicker at the edges.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (A)

$\mu = \frac{\mu_{g}}{\mu_{c}} = \frac{1.5}{1.65} < 1 $
As $\frac{1}{f} = \left(\mu-1\right)\left(\frac{1}{R_{1}} - \frac{1}{R_{2}}\right) $
$ \therefore f $ becomes negative.
Therefore, the lens behaves as a diverging lens.