ch 7 - Waves and Sound Flashcards Preview

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Flashcards in ch 7 - Waves and Sound Deck (58)
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1

sinusoidal waves

waves that may be transverse or longitudinal in which the individual particles oscillate back and forth with a displacement that follows a sinusoidal pattern.

2

transverse waves

those waves in which the direction of the particle oscillation is perpendicular to the propagation (movement) of the wave; ex are electromagnetic waves such as visible light, microwaves and x-rays

3

longitudinal waves

waves in which particles of wave oscillate parallel to the direction of propagation, oscillating in direction of energy transfer; ex sound waves

4

distance from one maximum (crest) of a wave to the next

wavelength represented by the upside down y

5

number of wavelengths passing a fixed point per second

frequency (f), measured in hertz (Hz) or cycles per second

6

propagation speed (v) of a wave

v = f x upside down y (propagation speed = frequency x wavelength

7

period equation (inverse of frequency)

T = 1/f. Period = 1/f, defines the number of seconds per cycle

8

angular frequency

fancy w = 2pi x f = (2pi)/T measured in radians per second

9

equilibrium position

central point around which waves oscillate

10

displacement (x)

in waves, describes how far a particular point on the wave is from the equilibrium position, vector quantity

11

amplitude (A)

maximum magnitude of displacement from the equilibrium position to the top of the crest or bottom of a trough, in a wave

12

phase difference

measure of how "in step" or "out of step" waves are. If in same place at same time with same amplitude, frequency and wavelength then phase difference = 0

13

principle of superposition

states that when waves interact with each other, the displacement of the resultant wave at any point is the sum of the displacements of the two interacting waves

14

constructive interference

in principle of superposition, when waves are perfectly in phase, the displacements are always the sum of the amplitudes of the two waves

15

destructive interference

in principle of superposition, when waves are perfectly out of phase, then the displacements are always the difference between the amplitudes of the two waves

16

travelling wave

moving wave from moving end of string or source to immobile end; if end is continuously moving waves will come back and still be going out and interfere with each other

17

standing waves

fluctuation of amplitude along fixed points along length of string or whatever waves are on;

18

nodes

points on something producing standing waves that remain at rest (where amplitude is constantly zero)

19

antinodes

points on something producing standing waves midway between the nodes that fluctuate with maximum amplitude

20

natural (resonant) frequencies

sounds that naturally come from certain objects

21

timbre

quality of sound; determined by the natural frequencies of an object

22

noise

scientifically it is produced by objects that vibrate at multiple frequencies that have no relation to one another

23

frequency range generally audible to health young adults

20 Hz to 20,000 Hz

24

forced oscillation

if a periodically varying force is applied to a system, the system will then be driven at a frequency equal to the frequency of the force

25

resonating system

occurs when the frequency of the periodic force is equal to a natural (resonant) frequency of the system; amplitude of the oscillation is at a max

26

damping (attenuation)

a decrease in amplitude of wave caused by an applied or nonconservative force

27

equation for speed of sound

v = square root of (B/fancy p) where B is bulk modulus, a measure of medium's resistance to compression (B increases from gas to liquid to solid), fancy p = density of the medium; fastest in a solid with low density and slowest in a gas with high density

28

approximate speed of sound in air

343 m/s

29

pitch

our perception of the frequency of sound

30

infrasonic waves

frequencies below 20 Hz