Phys Chapter 19 Vocab

Waves

an organized disturbance that travels with a well-defined wave speed. Periodic wiggle in both space and time

Mechanical waves

motion of a substance (wave in water) or sound or in air or tissue

Electromagnetic waves

light waves (no substance needed)

Vibration

periodic wiggle in time

Crests

high points of the wave

Troughs

low points of the wave

Amplitude

distance from the midpoint ot the crest or the trough. Difference between the average maximum values of an acoustic variable

Wavelength

distance from the top of one crest to the top of the next crest, or distance between successive identical parts of the wave

Frequency

How often a vibration occurs

Period

time to complete 1 vibration

Wave speed

describes how fast a disturbance moves through a medium. Related to frequency and wavelength of a wave

Transverse wave

Particles move perpendicular to the direction of the wave. Side to side movement

Longitudinal wave

particles move in the same direction as the wave. Backward and forward movement

Compressions

waves compressed

Rarefactions

stretched wave region between compressions

Wave interference

occurs when 2 or more waves interact with each other because they occur in the same place at the same time

Superposition principle

The displacement due to the interference of waves is determined by adding the disturbances produced by each wave

Constructive interference

When the crest of one wave overlaps the crest of another, their individual effects add together to produce a wave of increased amplitude

Destructive interference

When the crest of one wave overlaps the trough of another, the high part of one wave simply fills in the low part of another. So their individual effects are reduced or even canceled out

Nodes

regions of minimal or zero displacement with minimal or zero energy

Antinodes

regions of maximum displacement and maximum energy

Doppler effect

An increase in light frequency when a light source approaches you, OR a decrease in light frequency when a light source moves away from you. The change in frequency as a result of the motion between a sound source and the receiver

Blue shift

increase in light frequency toward the blue end of the spectrum

Red shift

decrease in light frequency toward the red end of the spectrum