Book cover for College Physics

College Physics

Eugenia Etkina, Michael Gentle, Alan Van Heuvelen

ISBN #9780321715357

1st Edition

2,258 Questions

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Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This section bridges classical electromagnetic theories and quantum physics by exploring phenomena that the classical wave model could not explain, such as black body radiation and the photoelectric effect. Planck’s quantization of energy and Einstein’s photon hypothesis introduced a new understanding of light as composed of discrete quanta. The derivations of photon energy, momentum, and the Compton effect underscore the dual wave-particle nature of light. These concepts not only resolved experimental contradictions but also paved the way for many modern applications in imaging, energy conversion, and electronics.

Learning Objectives

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Key Concepts

CONCEPT

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Example Problems

Example 1

Wavelength of radiation from a person If a person could be modeled as a black body, at what wavelength would his or her surface emit the maximum energy?

Example 2

(a) A surface at $27^{\circ} \mathrm{C}$ emits radiation at a rate of 100 $\mathrm{W}$ . At what rate does an identical surface at $54^{\circ} \mathrm{C}$ emit radiation? (b) Determine the wavelength of the maximum amount of radiation emitted by each surface.

Example 3

Maximum radiation wavelength from star, Sun, and Earth Determine the wavelengths for the following black body radiation sources where they emit the most energy: (a) A bluewhite star at 40,000 K; (b) the Sun at 6000 K; and (c) Earth at about 300 K.

Example 4

Star colors and radiation frequency The colors of the stars in the sky range from red to blue. Assuming that the color indicates the frequency at which the star radiates the maximum amount of electromagnetic energy, estimate the surface temperature of red, yellow, white, and blue stars. What assumptions do you need to make about white stars to estimate the surface temperature?

Example 5

Estimate the surface area of a 60-watt lightbulb filament. Assume that the surface temperature of the filament when it is plugged into an outlet of 120 V is about 3000 K and the power rating of the bulb is the electric energy/s it consumes (not what it radiates). Incandescent lightbulbs usually radiate in visible light about 10% of the electric energy that they consume.
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Step-by-Step Explanations

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Common Mistakes

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