CHAPTER 18 Study Guide

18.1 Electromagnetic Waves

Key Concepts

• Electromagnetic waves are produced when an electric charge vibrates or accelerates.

• Electromagnetic waves can travel through a vacuum as well as through matter. The speed of light in a vacuum, c, is $3.00 \times {10}^8 \mathrm{m}/\mathrm{s}$.

• Electromagnetic waves vary in wavelength and frequency.

• Electromagnetic radiation behaves sometimes like a wave and sometimes like a stream of particles.

• Light spreads out as it moves away from its source.

Vocabulary

electromagnetic waves, p. 533; electric field, p. 533; magnetic field, p. 533; electromagnetic radiation, p. 533; photoelectric effect, p. 537; photons, p. 537; intensity, p. 538

18.2 The Electromagnetic Spectrum

Key Concepts

• The electromagnetic spectrum includes radio waves, infrared waves, visible light, ultraviolet rays, X-rays, and gamma rays.

• Electromagnetic waves are used in communications, medicine, and industry.

Vocabulary

electromagnetic spectrum, p. 540; amplitude modulation, p. 541; frequency modulation, p. 541; thermograms, p. 543

18.3 Behavior of Light

Key Concepts

• Materials can be transparent, translucent, or opaque.

• When light strikes a new medium, it can be reflected, absorbed, or transmitted.

Vocabulary

transparent, p. 546; translucent, p. 547; opaque, p. 547; image, p. 547; regular reflection, p. 547; diffuse reflection, p. 547; mirage, p. 548; polarized light, p. 548; scattering, p. 549

18.4 Color

Key Concepts

• As white light passes through a prism, shorter wavelengths refract more than longer wavelengths, and the colors separate.

• The color of any object depends on what the object is made of and on the color of light that strikes the object.

• The primary colors of light are red, green, and blue.

• The primary colors of pigments are cyan, yellow, and magenta.

Vocabulary

dispersion, p. 551; primary colors, p. 552; secondary color, p. 552; complementary colors of light, p. 552; pigment, p. 553; complementary colors of pigments, p. 553

18.5 Sources of Light

Key Concepts

• Common light sources include incandescent, fluorescent, laser, neon, tungsten-halogen, and sodium-vapor bulbs.

• Each light source produces light in a different way.

Vocabulary

luminous, p. 558; incandescent, p. 558; fluorescence, p. 559; phosphor, p. 559; laser, p. 560; coherent light, p. 560

Thinking Visually

Web Diagram Copy the web diagram below onto a sheet of paper. Use information from the chapter to complete the diagram.

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