A plano-concave lens is made of glass of refr | vedclass

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(B) The power $P$ of a lens is given by the lens maker's formula: $P = \frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.For a pla

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$-0.5 \,D$

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(B) The power $P$ of a lens is given by the lens maker's formula: $P = \frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} ight)$.For a plano-concave lens, the first surface is plane $(R_1 = \infty)$ and the second surface is concave $(R_2 = -100 \,cm = -1 \,m)$.Given refractive index $\mu = 1.5$.Substituting the values: $P = (1.5 - 1) \left( \frac{1}{\infty} - \frac{1}{-1} ight)$.$P = (0.5) (0 + 1) = 0.5 \,D$.Wait, for a concave lens, the power must be negative. Let's re-evaluate the sign convention: For a plano-concave lens, light enters the plane surface first $(R_1 = \infty)$ and exits the concave surface $(R_2 = -R = -1 \,m)$.$P = (1.5 - 1) \left( \frac{1}{\infty} - \frac{1}{-1} ight) = 0.5 	imes 1 = +0.5 \,D$ (This is for a plano-convex). For a plano-concave lens, the curved surface is the first surface $(R_1 = -1 \,m)$ and the second is plane $(R_2 = \infty)$.$P = (1.5 - 1) \left( \frac{1}{-1} - \frac{1}{\infty} ight) = 0.5 	imes (-1) = -0.5 \,D$.

$A$ plano-concave lens is made of glass of refractive index $1.5$ and the radius of curvature of its curved face is $100 \,cm$. What is the power of the lens?

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