Deep Dive: T3B01
The correct answer is D: They are at right angles. In an electromagnetic wave, the electric field and magnetic field are at right angles (90 degrees) to each other. They are also both perpendicular to the direction of wave propagation. This is a fundamental property of electromagnetic waves. The electric field and magnetic field oscillate at right angles to each other, and both are perpendicular to the direction the wave is traveling. This creates a three-dimensional wave structure where the E-field, B-field, and propagation direction form three mutually perpendicular axes. This relationship is what makes electromagnetic waves self-propagating - the changing electric field creates the magnetic field, and vice versa.
Why Other Answers Are Wrong
Option A: Incorrect. The electric and magnetic fields travel at the same speed (speed of light). They don't travel at different speeds. Option B: Incorrect. The fields are not parallel. They are perpendicular (at right angles) to each other. Option C: Incorrect. The fields don't revolve in opposite directions. They oscillate perpendicular to each other and to the direction of propagation.
Exam Tip
E and B fields = Right angles. Remember: In an electromagnetic wave, the electric field and magnetic field are at right angles (90 degrees) to each other, and both are perpendicular to the direction of propagation.
Memory Aid
**E** and **B** = **E**ach **B**isects (think 'EB = EB' = Each Bisects, at right angles)
Real-World Example
When you transmit a radio signal, the electromagnetic wave has an electric field and a magnetic field. If the wave is traveling north, the electric field might oscillate east-west, and the magnetic field oscillates up-down. These two fields are at right angles to each other, and both are perpendicular to the northward direction of travel. This is the fundamental structure of all electromagnetic waves, including radio waves.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T3B
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T3B topic.