Chapter 34: Q. 26 (page 991)

Find the focal length of the planoconvex polystyrene plastic lens in FIGURE $EX 34.26$ .

Short Answer

Expert verified

The focal length of the planoconvex polystyrene plastic lens is $68 cm$ .

Step by step solution

Figure for foal length of lens

Figure is,

For surfaces convex toward the object, the radius of curvature $R$ is positive.

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

Calculation of focal length of lens

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

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

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.

$R_{1} \to \infty$

With $R_{2} = - 40$ , the second surface behaves as a concave surface.

Focal length is,

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

Substitute the following numerical values:

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

$\frac{1}{f} = \frac{59}{4000 cm}$

$f = \frac{4000}{59} cm = 68 cm$

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Find the focal length of the planoconvex polystyrene plastic lens in FIGURE $EX 34.26$ .

Short Answer

Step by step solution

Figure for foal length of lens

Calculation of focal length of lens

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Find the focal length of the planoconvex polystyrene plastic lens in FIGURE EX34.26.

Short Answer

Step by step solution

Figure for foal length of lens

Calculation of focal length of lens

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Physics Textbooks

Medical Physics

Oscillations

Energy Physics

Work Energy and Power

Atoms and Radioactivity

Physical Quantities And Units

Study anywhere. Anytime. Across all devices.

Find the focal length of the planoconvex polystyrene plastic lens in FIGURE $EX 34.26$ .