Ch. 7: Waves and Sound

Question 1

Transverse waves

Answer 1

Have oscillations of wave particles perpendicular to the direction of wave propagation

Question 2

Longitudinal waves

Answer 2

Have oscillations of wave particles parallel to the direction of wave propagation (e.g. sound waves)

Question 3

Displacement

Answer 3

x, in a wave refers to how far a point is from the equilibrium position, expressed as a vector quantity

Question 4

Amplitude

Answer 4

A, of a wave is the magnitude of its maximal displacement

Question 5

Crest

Answer 5

Maximum point of a wave (point of most positive displacement)

Question 6

Trough

Answer 6

Minimum point of a wave (point of most negative displacement)

Question 7

Wavelength

Answer 7

λ, distance between two crests or two troughs

Question 8

Frequency

Answer 8

f, number of cycles it makes per second, expressed in hertz (Hz)

Question 9

Angular Frequency

Answer 9

ω, another way of expressing frequency, expressed in radians/sec

Question 10

Period

Answer 10

T, number of seconds it takes to complete a cycle. Inverse of frequency

Question 11

Interference

Answer 11

Describes the ways in which waves interact in space to from a resultant wave

Question 12

Constructive interference

Answer 12

Occurs when waves are exactly in phase w each other. The amplitude of the resultant wave is equal to the sum of the amplitudes of the two interfering waves

Question 13

Destructive interference

Answer 13

Occurs when waves are exactly out of phase w each other. Amplitude of the resultant wave is equal to the diff in amplitude between two interfering waves

Question 14

Partially constructive and partially destructive interference

Answer 14

Occur when two waves are not quite perfectly in or out of phase w each other. Displacement of the resultant wave is equal to the sum of displacements of the two interfering waves

Question 15

Traveling waves

Answer 15

Have continuously shifting points of max and min displacement

Question 16

Standing waves

Answer 16

Produced by the constructive and destructive interference of two waves of the same frequency traveling in opposite directions in the same space

Question 17

Antinodes

Answer 17

Points of max oscillation

Question 18

Nodes

Answer 18

Points where there is no oscillation

Question 19

Resonance

Answer 19

Increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object

Question 20

Damping

Answer 20

Decrease in amplitude caused by an applied or nonconservative force

Question 21

Sound

Answer 21

Produced by mechanical disturbance of a material that creates an oscillation of the molecules in the material

Question 22

Sound propagation

Answer 22

Sound propagates through all forms of matter (but not a vacuum). Propagates fastest through solids, followed by liquids, and slowest through gases– within a medium, as density increases, the speed of sound decreases.

Question 23

Pitch

Answer 23

Of a sound, related to its frequency

Question 24

Doppler Effect

Answer 24

Shift in the perceived frequency of a sound compared to the actual frequency of the emitted sound when the source of the sound and its detector ae moving relative to one another

• the apparent frequency will be higher than the emitted frequency when he source and detector are moving toward each other
• the apparent frequency will be lower than the emitted frequency when the source and detector are moving away from each other
• the apparent frequency can be higher, lower, or equal to the emitted frequency when the 2 objects are moving in the same direction, depending on their relative speeds

Question 25

Shock waves (sonic booms)

Answer 25

Can form when the source is moving at or above the speed of sound

Question 26

Sound level

Answer 26

Related to its intensity, loudness or volume

Question 27

Intensity

Answer 27

Related to a wave’s amplitude, decreases over distance and some energy is lost to attenuation (damping) from frictional forces

Question 28

Open pipes

Answer 28

Strings and open pipes (open at both ends) support standing waves, and the length of the string or pipe is equal to some multiple of half-wavelengths

Question 29

Closed pipes

Answer 29

Closed at one end, also support standing waves, and the length of the pipe is equal to some odd multiple of quarter-wavelengths

Question 30

Ultrasound

Answer 30

Sound is used medically in ultrasound machines for both imaging (diagnostic) and treatment (therapeutic) purposes