Lesson: Propagating Electric and Magnetic Fields Physics • 9th Grade

In this lesson, we will learn how to model electromagnetic waves as propagating electric and magnetic fields.

Lesson Plan

Students will be able to

describe an electromagnetic wave as a transverse wave consisting of perpendicular electric fields and magnetic fields that vary with the same period and are in phase,
recognize that an electromagnetic wave is produced by an oscillation of an electric field or of a magnetic field,
recognize that an oscillation of an electric field is necessarily accompanied by an oscillation of a magnetic field and vice versa,
recognize that neither a constant current nor a uniformly moving magnet produce electromagnetic waves,
recognize that electromagnetic waves are produced by the oscillations of sources of static electric and magnetic fields,
recall that the speed of electromagnetic waves is determined by the electric permittivity and magnetic permeability of the medium the waves propagate in and .

Lesson Worksheet

Q1:

Electromagnetic waves propagate through rubber that has a refractive index of 1.5. The electric permittivity of the rubber is C²/N⋅m². What is the magnetic permeability of the rubber?

Q2:

Which of the following formulas correctly shows the relation between , the speed at which electromagnetic waves propagate through a medium; , the electric permittivity of the medium; and , the magnetic permeability of the medium?

Q3:

At what speed do electromagnetic waves propagate in a vacuum? Answer to two significant figures.