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Ch 34: Geometric Optics
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 34, Problem 42a

Repeat Exercise 34.41 using the same lenses except for the following changes: The second lens is a diverging lens having a focal length of magnitude 60.0 cm.

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Identify the given data: The first lens is a converging lens with a focal length \( f_1 \), and the second lens is a diverging lens with a focal length \( f_2 = -60.0 \ \text{cm} \). The object distance \( d_o \) for the first lens is the same as in Exercise 34.41. Assume the lenses are separated by a distance \( d \).
Calculate the image distance \( d_{i1} \) for the first lens using the lens equation: \( \frac{1}{f_1} = \frac{1}{d_o} + \frac{1}{d_{i1}} \). Rearrange to solve for \( d_{i1} \): \( d_{i1} = \left( \frac{1}{f_1} - \frac{1}{d_o} \right)^{-1} \).
Determine the object distance for the second lens, \( d_{o2} \), by considering the separation \( d \) between the lenses. If the image from the first lens is real, \( d_{o2} = d - d_{i1} \). If the image is virtual, \( d_{o2} = d + |d_{i1}| \).
Use the lens equation for the second lens to find the final image distance \( d_{i2} \): \( \frac{1}{f_2} = \frac{1}{d_{o2}} + \frac{1}{d_{i2}} \). Rearrange to solve for \( d_{i2} \): \( d_{i2} = \left( \frac{1}{f_2} - \frac{1}{d_{o2}} \right)^{-1} \).
Analyze the final image properties (real or virtual, upright or inverted, magnified or reduced) by calculating the magnification for each lens. The total magnification is the product of the magnifications of the two lenses: \( M = M_1 \cdot M_2 \), where \( M_1 = -\frac{d_{i1}}{d_o} \) and \( M_2 = -\frac{d_{i2}}{d_{o2}} \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lens Types

Lenses are optical devices that refract light to form images. There are two main types: converging (convex) lenses, which focus light to a point, and diverging (concave) lenses, which spread light rays apart. Understanding the type of lens used is crucial for predicting how it will affect the path of light and the characteristics of the resulting image.
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Focal Length

The focal length of a lens is the distance from the lens to the focal point, where parallel rays of light converge (for converging lenses) or appear to diverge from (for diverging lenses). It is a key parameter that determines the lens's power and the nature of the images formed. A shorter focal length indicates a stronger lens, while a longer focal length indicates a weaker lens.
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Lens Formula

The lens formula relates the object distance (u), image distance (v), and focal length (f) of a lens, expressed as 1/f = 1/v + 1/u. This equation is essential for analyzing lens systems, allowing us to calculate the position and nature of the image formed by the combination of lenses. It is particularly important when dealing with multiple lenses, as their combined effects must be considered.
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Related Practice
Textbook Question

A 1.20 cm tall object is 50.0 cm to the left of a converging lens of focal length 40.0 cm. A second converging lens, this one having a focal length of 60.0 cm, is located 300.0 cm to the right of the first lens along the same optic axis. Find the location and height of the image (call it I1) formed by the lens with a focal length of 40.0 cm.

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Textbook Question

BIO The Lens of the Eye. The crystalline lens of the human eye is a double-convex lens made of material having an index of refraction of 1.44 (although this varies). Its focal length in air is about 8.0 mm, which also varies. We shall assume that the radii of curvature of its two surfaces have the same magnitude. Find the radii of curvature of this lens.

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Textbook Question

An object is 16.0 cm to the left of a lens. The lens forms an image 36.0 cm to the right of the lens. Draw a principal-ray diagram.

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Textbook Question

Zoom Lens. Consider the simple model of the zoom lens shown in Fig. 34.43a. The converging lens has focal length f1 = 12 cm, and the diverging lens has focal length f2 = -12 cm. The lenses are separated by 4 cm as shown in Fig. 34.43a. (a) For a distant object, where is the of the converging lens? (c) Where is the final image? Compare your answer to Fig. 34.43a.

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Textbook Question

An object is 16.0 cm to the left of a lens. The lens forms an image 36.0 cm to the right of the lens. If the object is 8.00 mm tall, how tall is the image? Is it erect or inverted?

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Textbook Question

You wish to project the image of a slide on a screen 9.00 m from the lens of a slide projector. If the dimensions of the picture on a 35 mm color slide are 24 mm ✖ 36 mm, what is the minimum size of the projector screen required to accommodate the image?

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