### motion | wave:

Light wave
* All light waves are examples of electromagnetic waves
  - transverse waves
  - move at the speed of light
  - run precisely in phase with each other and are of the same colour
* All light waves travel at the same speed in a vacuum
  - in vacuum with same velocity
* Most light waves transfer energy.
* Some light waves have peaks that are closer together than other light waves.
* add when they are in phase and subtract when out of phase.
* are an example of transverse waves
  - brighter when the amplitude is higher
  - currents alternating trillions of times per second
* are electromagnetic or non-mechanical waves which can propagate through vacuum
  - far larger than the size of the nucleus
  - fluctuations of electric and magnetic fields in space
* behave in the same way.
* bend as they pass by the edge of a narrow aperture or slit.
* can even travel like a twisting corkscrew
  - move through space
  - pass through some materials, while other materials block light
  - travel through empty space
* consist of oscillating magnetic and electric fields.
* have 'crests' and 'troughs'
  - intensity just as sound waves do
  - much in common with mechanical waves, they share a lot of mathematics
* move through air in straight lines.
* reach the retina, and only particular wavelengths.
* reflect from the apple towards a photographic film
  - surfaces of two plastic sheets separated by a thin air gap
* slow down when they travel inside substances, such as air, water, glass or a diamond.
* travel faster than radio waves
  - in a straight line unless they meet an obstacle
  - out from their source in straight lines called rays
* traveling freely can vibrate in any direction.
* wash past atomic-scale features, like ocean waves rolling over seashells.
+ A Brief History of Time, Summary, Chapter 4: 1988 books :: Science books
  * Light waves have 'crests' and 'troughs'. The highest point of a wave is the crest, and the lowest part of the wave is a trough. Sometimes more than one of these waves can  with each other - the crests and the troughs line up. This is called 'light interference'. When light waves interfere with each other, this can make many colors. An example of this is the colors in soap bubbles.
+ Wave (physics), Types: Wave physics
  * Light waves can move through space. The nature of light is a big part of quantum mechanics.

Longitudinal wave
* are waves which travel in the same direction as their disturbance.
* cause the medium particles to move parallel to the direction of wave propagation
  - to move parallel to the direction of thewave
* have compressions and rarefactions.
* require a medium that can be compressed.
* travel the medium in the direction they propagate.
  * Longitudinal waves have compressions and rarefactions. Compressions and rarefactions move along a travelling longitudinal wave.

Magnetic wave
* can damage computers.
* penetrate the skin, fatty tissues and bones, invigorating the organs.

Matter wave
* arise in quantum mechanical description of nature.
* provide an explanation for the arrangement of electrons in separate orbits.

### motion | wave:

Mechanical wave
* Any mechanical wave is composed of discrete particles of material.
* Most mechanical waves result from vibration.
  * are a local oscillation of material. Therefore, mechanical waves transport energy and not material
  - of two types i.e. transverse waves and longitudinal waves
* involve disturbances of a mechanical medium such as air, water, earth, and space.
* require a medium in order to transport their energy from one location to another.
* transfer energy through matter called the medium.
* transport energy through a medium.