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Chapter 4

Chapter 4: Light

Study Plan

Unlike the physicist or the chemist, who has control over the conditions in a laboratory, the astronomer must try to glean the secrets of the universe from the light and other particles that reach us from distant objects. On this leg of our journey we turn our attention to light, a most informative messenger, and find that

  • Light is an electromagnetic wave with a spectrum extending far beyond the colors of the rainbow.
  • Light is also a stream of particles called photons.
  • Reconciling the two identities of light and matter-its wave and particle characteristics-challenges our everyday ideas about what is "real."
  • The wave-particle nature of light and matter gives different types of atoms unique spectral "fingerprints" that we can use to measure the composition and properties of distant objects.
  • Temperature measures the thermal energy of an object and determines the amount and spectrum of light that a dense object emits.
  • Light is not only a messenger but also a means by which energy is carried throughout the universe.

Organize

  • Read Chapter 4 in your textbook or ebook.
  • Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

  • Access the Animations given for this chapter. These brief lessons enhance your understanding of core concepts.
  • Access the applets for this chapter.  Be sure to try different parameters with the applets to make sure you understand the concepts.
  • Use the FlashCards to test your memory for new terms.
  • Work the "Thinking about the Concepts" and "Applying the Concepts" questions in the end of chapter review materials.
  • If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.
  • For more details on the mathematical formulas used in this chapter, review the three Math Tools boxes:
    • Math Tools 4.1, Working with Electromagnetic Radiation
    • Math Tools 4.2, Making Use of the Doppler Effect
    • Math Tools 4.3, Working with the Stefan-Boltzmann and Wien's Laws

Connect

  • Periodic Connections boxes and the Seeing the Forest through the Trees section at the chapter's end draw your attention to recurring themes and help prepare you for concepts explored more fully in subsequent chapters.
  • Visit Astronomy in the News for breaking news of new discoveries and the opportunity to apply what you've learned in this chapter to real-world (and real Universe) events.
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