Chapter 34: Q. 28 (page 991)

Find the focal length of the meniscus polystyrene plastic lens in FIGURE $EX 34.28$ .

Short Answer

Expert verified

The focal length of meniscus polystyrene plastic lens is $203 cm$ .

Step by step solution

Formula for focal length

The lens-makers' equation gives the inverse of the focal length of a narrow lens surrounded by air.

$\frac{1}{f} = (n - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

For surfaces convex toward the object, the radius of curvaturelocalid="1649148884725" $R$ is positive.

For surfaces that are concave toward the object, the radius of curvature localid="1649148894449" $R$ is negative.

Calculation of focal length of lens

Assuming the object is on the left, the lens's initial surface is planar, and we can think of it as a part of a sphere with $R = - 40 cm$ .

With $R = - 30 cm$ , the second surface serves as a concave surface.

The focal length of the lens is,

$\frac{1}{f} = (n - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

Substitute the following numerical values:

$\frac{1}{f} = (1.59 - 1) (\frac{1}{- 40 cm} - \frac{1}{30 cm})$

$\frac{1}{f} = \frac{59}{12000 cm}$

$f = \frac{12000}{59} cm = 203 cm$

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Find the focal length of the meniscus polystyrene plastic lens in FIGURE $EX 34.28$ .

Short Answer

Step by step solution

Formula for focal length

Calculation of focal length of lens

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Find the focal length of the meniscus polystyrene plastic lens in FIGURE EX34.28.

Short Answer

Step by step solution

Formula for focal length

Calculation of focal length of lens

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Physics Textbooks

Translational Dynamics

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Energy Physics

Rotational Dynamics

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Study anywhere. Anytime. Across all devices.

Find the focal length of the meniscus polystyrene plastic lens in FIGURE $EX 34.28$ .