A plane electromagnetic wave is moving through vacuum toward the east
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
A plane electromagnetic wave is moving through vacuum toward the east, which you may take to be the +x–direction. At the instant shown, the electric field vector at the origin points straight upward along the +z–axis.
Assume the wave is a uniform plane wave and that no other information about field magnitudes is needed.
(a) Identify the direction of the magnetic field vector at the origin at the instant described. Express your answer as a unit–vector direction (e.g., ^, −^, etc.).
(b) Justify your answer in part (a) by describing the geometric relationships among the electric field, the magnetic field, and the direction of propagation for a plane electromagnetic wave in free space.
(c) Suppose instead that the wave were traveling due west while the electric field still pointed upward along +z. State and explain the new direction of the magnetic field at the origin.