The Physics
Hypertextbook
Opus in profectus

# Electromagnetic Spectrum

## Summary

• The term electromagnetism is a blanket term for all possible types of interactions that can exist between electric charges.
• Electricity and magnetism are related phenomena, however when…
• charges are at rest the phenomena are generally described as electric or electrostatic
• The source of all electric phenomena is electric charge.
• charges are in motion and the magnitude of the current is constant the phenomena are generally described as magnetic or magnetostatic
• The source of all magnetic phenomena is moving electric charge.
• charges are in motion and the magnitude of the current is varying with time the phenomena are generally described as electromagnetic
• The source of all electromagnetic phenomena is accelerating electric charge.
• Forces
• Charged objects exert electric forces on one another (sometimes called electrostatic forces).
• This is the principle behind static cling and why electrons are bound to the nucleus of an atom.
• Magnets exert magnetic forces on one another.
• This is the principle behind compasses and refrigerator magnets.
• Magnets exert magnetic forces on moving charges.
• This is the principle behind electric motors and electric generators.
• Fields
• Electric charges are surrounded by an electric field.
• Moving electric charges are also surrounded by a magnetic field.
• Electric current flowing through a coil of wire is an electromagnet.
• The spin of the electron makes it behave like a very small magnet.
• Electric currents in the molten outer core of the Earth make it behave like a giant magnet.
• Time varying fields
• A changing electric field will produce a magnetic field.
• A changing magnetic field will produce an electric field.
• Waves
• An electromagnetic wave is any disturbance in the electric and magnetic fields that propagates.
• All electromagnetic waves propagate at the speed of light in a vacuum.
• The seemingly disparate phenomena of electricity, magnetism, and optics are all related aspects of the larger phenomenon of electromagnetism.
• This last statement was predicted mathematically before it was determined experimentally.
• Electromagnetic waves can have any wavelength or frequency.
• Light is an electromagnetic wave that is visible to the typical human eye.
• There are electromagnetic waves other than light.
• The full range of frequencies or wavelengths of electromagnetic waves is called the electromagnetic spectrum.
• The currently agreed upon, major named bands of the electromagnetic spectrum are, in order of increasing frequency