(A) The power of a lens is given by the formula $P = \frac{1}{f}$,where $f$ is the focal length in meters.Given power $P = -4.0 \text{ D}$.Since the p

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Concave lens of focal length $-25.0 \text{ cm}$

(A) The power of a lens is given by the formula $P = \frac{1}{f}$,where $f$ is the focal length in meters.Given power $P = -4.0 \text{ D}$.Since the power is negative,the lens is a concave lens.Using the formula $f = \frac{1}{P}$,we get:$f = \frac{1}{-4.0} \text{ m} = -0.25 \text{ m}$.Converting meters to centimeters: $f = -0.25 \times 100 \text{ cm} = -25.0 \text{ cm}$.Therefore,it is a concave lens with a focal length of $-25.0 \text{ cm}$.

Class 12 Physics Ray Optics and Optical Instruments Refraction by Lenses

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$A$ lens has a power of $-4.0 \text{ Diopter}$. This means . . . . . . .

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Concave lens of focal length $-25.0 \text{ cm}$
B
Concave lens of focal length $-0.25 \text{ cm}$
C
Concave lens of focal length $+0.25 \text{ cm}$
D
Concave lens of focal length $+25.0 \text{ cm}$

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Ray Optics and Optical Instruments

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Refraction by Lenses

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DifficultAIIMS 2008

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MediumJEE MAIN 2025

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$A$ double convex lens of focal length $20 \ cm$ is made of glass of refractive index $3/2$. When placed completely in water $(_{a}\mu_{w} = 4/3)$,its focal length will be.....$cm$.

EasyAIPMT 1990

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$A$ lens has a power of $-4.0 \text{ Diopter}$. This means . . . . . . .

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For a concave lens of focal length $f$,the relation between object distance $u$ and image distance $v$ from its pole can best be represented by ($u = v$ is the reference line):

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