College Physics Explore and Apply

Eugenia Etkina; Alan Van Heuvelen; Gorazd Planinši?

ISBN #9780134601823

2nd Edition

2,244 Questions

46,660 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

This chapter bridges classical and quantum physics by examining how black body radiation and the photoelectric effect challenge classical electromagnetic theory. It introduces key concepts like Stefan-Boltzmann’s law, Wien’s law, and Einstein’s photoelectric equation, emphasizing the quantization of light into photons with both wave-like and particle-like properties. The discussion extends to photon momentum, applications in X-ray technology, and modern devices such as photocells, solar cells, and LEDs, thereby highlighting the profound impact of quantum optics on both fundamental physics and practical technology.

Learning Objectives

Key Concepts

CONCEPT

DEFINITION

Atomic Physics

The study of atomic models and structure, detailing the evolution from classical orbit models (e.g., Bohr’s model) to quantum mechanics with quantized energy levels, quantum numbers, the uncertainty principle, and tunneling.

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

Determine the wavelengths for the following black body radiation sources where they emit the most energy: (a) A blue-white star at $40,000 \mathrm{~K}$; (b) the Sun at $6000 \mathrm{~K}$ and (c) Earth at about $300 \mathrm{~K}$.

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 $120 \mathrm{V}$ is about $3000 \mathrm{K}$ and the power rating of the bulb is the electric energy it consumes (not what it radiates). Incandescent lightbulbs usually radiate in visible light about $10 \%$ of the electric energy that they consume.