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Ch 34: Ray Optics
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 34, Problem 53

An astronaut is exploring an unknown planet when she accidentally drops an oxygen canister into a 1.50-m-deep pool filled with an unknown liquid. Although she dropped the canister 21 cm from the edge, it appears to be 31 cm away when she peers in from the edge. What is the liquid's index of refraction? Assume that the planet's atmosphere is similar to earth's.

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Step 1: Understand the problem. The apparent position of the canister is distorted due to refraction of light as it passes from the liquid to the atmosphere. The index of refraction of the liquid can be calculated using the relationship between the real depth and the apparent depth.
Step 2: Recall the formula for the index of refraction: \( n = \frac{d_{real}}{d_{apparent}} \), where \( d_{real} \) is the actual depth of the object and \( d_{apparent} \) is the depth as it appears to the observer.
Step 3: Identify the given values. The real depth of the canister is \( d_{real} = 1.50 \, \text{m} \). The apparent depth can be calculated using the ratio of the apparent distance to the real distance horizontally: \( d_{apparent} = \frac{31 \, \text{cm}}{21 \, \text{cm}} \times d_{real} \).
Step 4: Substitute the values into the formula for \( d_{apparent} \): \( d_{apparent} = \frac{31}{21} \times 1.50 \, \text{m} \). This gives the apparent depth of the canister.
Step 5: Use the formula for the index of refraction \( n = \frac{d_{real}}{d_{apparent}} \) and substitute \( d_{real} = 1.50 \, \text{m} \) and the calculated \( d_{apparent} \) to find the index of refraction of the liquid.

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Key Concepts

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

Refraction

Refraction is the bending of light as it passes from one medium to another with a different density. This phenomenon occurs because light travels at different speeds in different materials. The degree of bending is described by Snell's Law, which relates the angles of incidence and refraction to the indices of refraction of the two media.
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Index of Refraction

Index of Refraction

The index of refraction (n) is a dimensionless number that describes how much light slows down in a medium compared to its speed in a vacuum. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium. A higher index indicates that light travels slower in that medium, affecting how objects appear when viewed through it.
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Geometric Optics

Geometric optics is the branch of optics that describes light propagation in terms of rays. It simplifies the study of light behavior by ignoring wave properties and focusing on the paths that light rays take. This approach is particularly useful for analyzing situations involving lenses, mirrors, and refraction, such as the scenario of the astronaut observing the canister in the liquid.
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Related Practice
Textbook Question

A 4.0-m-wide swimming pool is filled to the top. The bottom of the pool becomes completely shaded in the afternoon when the sun is 20° above the horizon. How deep is the pool?

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Textbook Question

Shown from above in FIGURE P34.54 is one corner of a rectangular box filled with water. A laser beam starts 10 cm from side A of the container and enters the water at position x. You can ignore the thin walls of the container. If x = 15 cm, does the laser beam refract back into the air through side B or reflect from side B back into the water? Determine the angle of refraction or reflection.

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Textbook Question

Shown from above in FIGURE P34.54 is one corner of a rectangular box filled with water. A laser beam starts 10 cm from side A of the container and enters the water at position x. You can ignore the thin walls of the container. Find the minimum value of x for which the laser beam passes through side B and emerges into the air.

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Textbook Question

A horizontal laser beam enters the glass prism shown in FIGURE P34.55. When the laser beam exits the prism, by what angle will it have been deflected from horizontal?

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Textbook Question

The 80-cm-tall, 65-cm-wide tank shown in FIGURE P34.48 is completely filled with water. The tank has marks every 10 cm along one wall, and the 0 cm mark is barely submerged. As you stand beside the opposite wall, your eye is level with the top of the water. Can you see the marks from the top of the tank (the 0 cm mark) going down, or from the bottom of the tank (the 80 cm mark) coming up? Explain.


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Textbook Question

A horizontal meter stick is centered at the bottom of a 3.0-m-deep, 3.0-m-wide pool of water. Suppose you place your eye just above the edge of the pool and look along the direction of the meter stick. What angle do you observe between the two ends of the meter stick if the pool is (a) empty and (b) completely filled with water?

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