AIIMS 2018 Physics Refraction through lenses Assertion Reason Question

The assertion is false because when a convex lens is immersed in water (with a refractive index μ₉ = 3/2), its effective focal length is given by the formula $f' = \frac{f}{\mu - 1}$, where $\mu$ is the refractive index of the lens material relative to the medium. In this case, the focal length in water would be $f' = \frac{f}{\frac{3}{2} - 1} = \frac{2f}{1/2} = 4f$, not $\frac{4}{3}f$ as stated. The reason is also false because it incorrectly states that the focal length becomes $3f$, which is not consistent with the calculations. Thus, both the assertion and reason are incorrect, making option D the correct choice. Other options are incorrect as they imply either assertion or reason is true or that reason explains assertion, which is not the case.