alma 6th unit 2 waves

Wave

A wave is a disturbance, vibration or movement of molecules that carries energy from place to place.

What waves transmit

Waves transmit energy, not matter. Again, a wave does NOT carry matter with it! A wave moves the matter as it goes through it.

Three ways waves and light can be modified

refracted (bend), reflected (bounce), absorbed (block)

Electromagnetic waves

Some waves do not need matter ( a “medium”) to be able to move (for example, through space). These are electromagnetic waves. This includes light. (But more on that in 8th grade!)

Mechanical waves

Some waves MUST have a medium in order to move. These are called mechanical waves.

Optics

The study of how light can be reflected, refracted and absorbed, as well as diffracted, diffused and polarized is called optics.

Who discovered the field of optics

The field of optics was discovered by Isaac Newton (yes that same guy).

Two types of waves

Transverse waves and Longitudinal waves

Transverse waves

Transverse waves, like a guitar string, have particles that move perpendicular to the motion of the wave. The wave propagates left to right while the particles move up and down.

Longitudinal waves

Longitudinal waves, like a slinky or a spring, have particles that move parallel to the motion of the wave. The wave propagates left to right and the particles move left and right.

What wave properties depend on

Wave properties depend on what (type of energy) is making the waves.

Wavelength

The distance between one point on a wave and the exact same place on the next wave. Wavelength is measured in meters.

Frequency

How many waves go past a point in one second, or how frequently a wave passes a certain point. The unit of measurement is hertz (Hz). Frequency is abbreviated f. The higher the frequency, the more energy in the wave.

Amplitude

How far the medium moves from rest position (where it is when not moving). The amplitude is the strength, or the height, of the wave. A higher amplitude is stronger than a lower amplitude wave. For visible light, a high amplitude wave would be brighter than a lower amplitude wave. Visible light brightness is measured in lumens. Sound wave amplitude is measured in decibels.

Compression

The part of a longitudinal wave where the particles or coils are pushed close together.

Rarefaction

The part of a longitudinal wave where the particles or coils are spread farther apart.