Waves: Mechanical and Electromagnetic

Study Notes

Waves are disturbances produced by vibrating particles of matter. They transfer energy as they propagate through a medium or space.
Waves are classified in two ways: (1) how they propagate, and (2) the orientation of the wave propagation relative to the direction of energy transfer.
Waves can be either mechanical or electromagnetic, based on their ability to transmit energy through a vacuum.

Mechanical waves propagate only when a medium is available.
Examples include: sound waves (which travel fastest in solids), water waves, seismic waves, stadium waves, slinky waves, string waves, and jump rope waves.

Electromagnetic waves can travel without a medium.
They are produced by the vibration of charged particles.
There are seven types of electromagnetic waves, arranged from increasing frequency or decreasing wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Radio waves are used for transmitting radio and TV signals.
Microwaves are used in microwave ovens and cellular phone communication.
Infrared waves have medical applications in detecting heat leaks.
Visible light is the only electromagnetic wave detectable by the naked eye. Colors in a rainbow correspond to different wavelengths in the electromagnetic spectrum.
Ultraviolet waves are blocked by the ozone layer; overexposure can cause skin cancer.
X-rays can penetrate most matter and are used in medical imaging.
Gamma rays are more penetrating than X-rays and are also used in medical applications.

The direction of energy transfer relative to the wave's direction is an additional way to classify waves; they can be longitudinal or transverse.
Longitudinal waves: The energy travels parallel to the direction of the wave. These waves consist of compressions and rarefactions.
- Compressions are regions where particles are closest to each other.
- Rarefactions are regions where particles are furthest from each other.
- Sound waves and earthquake waves are examples of longitudinal waves.
Transverse waves: The energy travels perpendicular to the direction of the wave. These waves include crests (highest point), troughs (lowest point), amplitudes (maximum displacement from the origin), and wavelengths (distance between two consecutive points in a wave).
- Examples include electromagnetic waves, water waves, and string waves.