phys_WAVES & SOUND

wave

a traveling disturbance of coordinated vibrations that transmit energy with no net movement of matter.

Mechanical waves

require a medium

Electromagnetic waves

don't need a medium- travel through electric and magnetic field lines

pulse

a single "bump" of a wave

continuous or periodic wave

caused by a repetitive oscillation

amplitude

maximum displacement from equilibrium

trough

negative amplitude - maximum negative displacement from equilibrium

wavelength

distance between two repetitive points of a wave

transverse wave

motion of particles is perpendicular to motion of wave

think sine graph

longitudinal wave

motion of particles is parallel to motion of wave

reflection

wave hits obstacle and goes back to where it came from

law of reflection

angle of incidence = angle of reflection

interferance

occurs when more than 1 wave passes through the same region of a medium

principle of superposition

end result of wave combination is algerbraic sum of individual displacements caused by the waves

standing wave

wave appears to be at rest because it is interfering with itself

nodes

point of no displacement

antinodes

point of maximum displacement

fundamental frequency

lowest natural frequency of a standing wave

overtones

other natural frequencies

harmonics

overtones that are integer multiples of the fundamental

Refraction

waves hit an obstacle and are reflected at an angle

diffraction

waves bend around obstacles in their path

pitch

determined by frequency of a source; how high or low we perceive a source to be

infrasonic

less than 20 Hz;

ultrasonic

more than 20,000 Hz

Intensity

energy transferred per unit area of sound wave

Beats

caused by interference patterns of similar frequencies

Beat f = abs (f2-f1)

Doppler effect

result of relative motion between a source of sound and a listener

faster objects moving apart; lower frequency appears

Supersonic speed

faster than sound

Mach #

mach 3 = traveling at 3x the speed of sound

shock wave

barrier formed by crests of sound waves when object travels faster than the speed of sound

sound barrier

same as shock wave; object travels faster than sound and its own piled up sound waves form a barrier