Connection for ap® courses

Electromagnetic waves are all around us. The beauty of a coral reef, the warmth of sunshine, sunburn, an X-ray image revealing a broken bone, even microwave popcorn—all involve electromagnetic waves . The list of the various types of electromagnetic waves, ranging from radio transmission waves to nuclear gamma-rays (γ-rays), is interesting in itself. Even more intriguing is that all of these widely varied phenomena are different manifestations of the same thing—electromagnetic waves. (See [link] .)

What are electromagnetic waves? How are they created, and how do they travel? How can we understand and conceptualize their widely varying properties? What is their relationship to electric and magnetic effects? These and other questions will be explored in this chapter.

Electromagnetic waves support Big Idea 6 that waves can transport energy and momentum. In general, electromagnetic waves behave like any other wave, as they are traveling disturbances (Enduring Understanding 6.A). They consist of oscillating electric and magnetic fields, which can be conceived of as transverse waves (Essential Knowledge 6.A.1). They are periodic and can be described by their amplitude, frequency, wavelength, speed, and energy (Enduring Understanding 6.B).

Simple waves can be modeled mathematically using sine or cosine functions involving the wavelength, amplitude, and frequency of the wave. (Essential Knowledge 6.B.3). However, electromagnetic waves also have some unique properties compared to other waves. They can travel through both matter and a vacuum (Essential Knowledge 6.F.2), unlike mechanical waves, including sound, that require a medium (Essential Knowledge 6.A.2).

Maxwell’s equations define the relationship between electric permittivity, the magnetic permeability of free space (vacuum), and the speed of light, which is the speed of propagation of all electromagnetic waves in a vacuum. This chapter uses the properties electric permittivity (Essential Knowledge 1.E.4) and magnetic permeability (Essential Knowledge 1.E.5) to support Big Idea 1 that objects and systems have certain properties and may have internal structure.

The particular properties mentioned are the macroscopic results of the atomic and molecular structure of materials (Enduring Understanding 1.E). Electromagnetic radiation can be modeled as a wave or as fundamental particles (Enduring Understanding 6.F). This chapter also introduces different types of electromagnetic radiation that are characterized by their wavelengths (Essential Knowledge 6.F.1) and have been given specific names (see [link] ).

Big Idea 1 Objects and systems have properties such as mass and charge. Systems may have internal structure.

Enduring Understanding 1.E Materials have many macroscopic properties that result from the arrangement and interactions of the atoms and molecules that make up the material.