Kerala KEAM 5 June 2024 Solved Paper

The power $P$ of a lens is related to its focal length $f$ by the equation:$$P = \frac{1}{f}$$where:- $P$ is the power of the lens in diopters (D),- $f$ is the focal length of the lens in meters.We are given that the power of the lens is $P = -2.0 \, D$. The negative sign indicates that the lens is a concave lens (since concave lenses have negative focal lengths).Using the formula for power:$$P = \frac{1}{f}$$Substitute the value of $P$:$$-2.0 = \frac{1}{f}$$Solving for $f$:$$f = \frac{1}{-2.0} = -0.5 \, m = -50 \, cm$$Thus, the focal length of the lens is $-50 \, cm$, and since the focal length is negative, the lens is a concave lens.Therefore, the correct answer is:$$\boxed{B) Concave lens, 50 cm}$$ Quick Tip: A negative power indicates a concave lens, and the focal length is negative for concave lenses. The relationship $P = \frac{1}{f}$ allows you to easily calculate the focal length from the power.