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physics ch 25 waves
wave motion
Question | Answer |
---|---|
vibration | a repeating back and forth motion about an equilibrium position |
wave | a disturbance that is transmitted progressively form one place to the next with no actual transport of matter (the source of all waves is something that vibrates) |
period | time of a back and forth swing of the pendulum (period = 1/frequency) |
simple harmonic motion | the back and forth vibratory motion (oscillatory motion) of a swinging pendulum |
sine curve | a pictorial representation of a wave |
crest | the high point on a wave |
trough | low points on a wave |
amplitude | the distance from the midpoint to the crest (or trough) of the wave (maximum displacement from equilibrium) |
wavelength | the distance from the top of one crest to the top of the next one (or the distance between successive identical parts of the wave); wavelength x frequency = speed of wave; symbol is lambda |
frequency | number of vibrations an object makes in a unit of time; the number of back and forth vibrations an object makes in a given time (usually one second); a complete back and forth vibration is one cycle; (frequency =1/period) |
hertz | the unit of frequency; one cycle per second is one hertz |
transverse wave | when the motion of the medium is at right angles to the direction in which the wave travels. examples include waves in stretched strings of instruments and electromagnetic waves of radio waves and light |
longitudinal wave | particles move back and forth (oscillate parallel to or along with) in the same direction in which the wave travels; example includes sound waves |
interference pattern | a regular arrangement of places where wave effects are increased, decreased or neutralized; occur when waves from different sources arrive at the same point at the same time. |
constructive interference | the crest of one wave overlaps the crest of another and their individual effects add together |
destructive interference | the crest of one wave overlaps the trough of another and their individual effects are reduced (high part of one wave fills low part of another wave = cancellation) |
out of phase | the crests of one wave overlap the troughs of another to produce regions of zero amplitude |
in phase | the crests of one wave overlap the crests of the other, and the troughs overlap as well. |
standing wave | a standing wave is a wave that appears to stay in one place - it does not appear to move through the medium; certain parts of a standing wave remain stationary |
node | the stationary ponts on a standing wave |
antinodes | positions on a standing wave with the largest amplitudes |
Dopper effect | apparent change in frequency due to th emotion of the source (or receiver). The greater the speed of the source, the greater the Doppler effect. |
blue shift | an increase in frequency because the increase is toward the high-frequency or blue end of the color spectrum |
red shift | decrease in frequency; refers to the low-frequency of red end of the color spectrum (distant galaxies show red shift that shows speed of recession) |
bow wave | crests overlap at the edges and the pattern made by these overlapping crests is a V shape; occurs when a wave source moves faster than the waves it produces |
shock wave | a three-dimensional wave that consists of overlapping spheres that form a cone; occurs when an object moves faster than the speed of sound |
sonic boom | the sharp crack heard when the shock wave that sweeps behind a supersonic aircraft reaches the listeners |