The Development of Electromagnetic Wave Theory

Vocabulary flashcards covering key terms and figures from the development of electromagnetic wave theory.

Electromagnetic waves

Disturbances that transfer energy through a field, are transverse, do not require a medium, and propagate at the speed of light in vacuum; produced by accelerating electric charges; composed of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation.

Transverse wave

A wave in which oscillations are perpendicular to the direction of travel (as in EM waves), in contrast to longitudinal (compressional) waves.

Longitudinal (compressional) waves

Waves in which oscillations are parallel to the direction of travel (e.g., sound waves).

Speed of light (c)

The constant speed that EM waves travel in vacuum, approximately 3 x 10^8 meters per second.

Electromagnetic spectrum

The range of all possible frequencies of electromagnetic radiation, including radio waves, microwaves, infrared, visible light, ultraviolet, and X-rays.

Electric field

A field surrounding electric charges that exerts force; in EM waves, it oscillates and interacts with the magnetic field.

Magnetic field

A field surrounding magnets or moving charges; in EM waves, it oscillates and is perpendicular to the electric field.

Perpendicular (orthogonal) fields

In an EM wave, the electric and magnetic fields oscillate at right angles to each other and to the direction of propagation.

Oscillation

Periodic variation of a quantity; in EM waves, the electric and magnetic fields continuously oscillate.

Vacuum

Space devoid of matter; EM waves propagate in vacuum at the constant speed c.

Electromagnetic induction

Induction of electric current by a changing magnetic field; fundamental to the operation of generators and transformers (Faraday's law).

Ampère (André-Marie Ampère)

Showed that a current-carrying wire behaves like a magnet and mathematically developed Ampère’s law describing the magnetic force between currents.

Faraday (Michael Faraday)

Demonstrated electromagnetic induction; showed that a changing magnetic environment induces current; foundational to transformers and generators.

Hertz (Heinrich Rudolf Hertz)

Demonstrated the existence of electromagnetic waves by producing and detecting EM radiation; studied reflection, refraction, polarization, interference, and velocity.

Maxwell (James Clerk Maxwell)

Formulated that a changing electric field can produce a magnetic field and vice versa; proposed that EM waves travel at the speed of light and linked electricity with magnetism.

Oersted (Hans Christian Ørsted)

Showed that a current-carrying wire produces a magnetic field, linking electricity and magnetism, and deflecting a compass needle.

Wavelength–frequency relationship

For EM waves, speed = frequency × wavelength; in vacuum, this speed equals c.

Polarization

Property describing the orientation of the electric field in an EM wave; studied and demonstrated by Hertz.

Electric field vs. magnetic field in EM waves

In an EM wave, the electric and magnetic fields oscillate perpendicularly to each other and to the direction of wave propagation.

Produced by accelerating electrons

EM waves are generated when electrons accelerate, changing the surrounding electric and magnetic fields.