Exam 1

Question 1

what do waves carry?

Answer 1

energy and information by propagation

Question 2

define longitudinal wave

Answer 2

when the disturbance is in the direction of propagation

Question 3

define transverse wave

Answer 3

when the disturbance is perpendicular to the direction of propagation

Question 4

which types of waves don’t require a medium to propagate in?

Answer 4

light waves

Question 5

define amplitude

Answer 5

maximum displacement of a point from its equilibrium position

Question 6

define wave speed

Answer 6

the speed (v) at which the disturbance travels

Question 7

define wave velocity

Answer 7

velocity at which the wave (one of its peaks) travels in the direction of propagation

it is a vector in the direction of propagation with magnitude v

Question 8

define period

Answer 8

the period (T) is the time it takes for a point on the wave to go through one complete cycle of oscillation

Question 9

define frequency

Answer 9

the frequency (f) of a wave is the number of complete cycles that pass through one point per unit time

Question 10

what 5 parameters are waves characterized by?

Answer 10

amplitude
frequency
period
wavelength
wave velocity

Question 11

what can harmonic/sinusoidal waves be described by?

Answer 11

a sine or cosine function

Question 12

define the superposition principle

Answer 12

if 2+ traveling waves overlap, the resultant disturbance (wave) is the sum of the disturbances of the individual waves

*good assumption for small waves

Question 13

when are phase differences valid?

Answer 13

for two harmonic waves with identical wavelength and frequency with a shift of delta x between them

Question 14

define collinear waves

Answer 14

when two otherwise identical waves with a phase difference travel in the same direction, the resulting wave has the same f and wavelength but the A depends on the phase shift

Question 15

define out of phase waves

Answer 15

two waves with ID A and wavelength and a phase shift of pi between them travel in the same direction

the resultant wave’s amplitude is 0!
this is called destructive interference

Question 16

define destructive interference

Answer 16

when the phase shift = pi, 3pi, 5pi, etc…
Amplitude of two waves with ID A and wavelength with this phase shift will have a resulting wave amplitude of 0

Question 17

constructive interference

Answer 17

when the phase shift = 0, 2pi, 4pi, etc

the sum of the wave’s amplitude will be 2A

Question 18

Closed ended wave

Answer 18

the reflection of the wave will be inverted; destructive interference

Question 19

open ended wave

Answer 19

reflected wave will not be inverted; constructive interference

Question 20

phase shift from a closed end

Answer 20

a periodic wave that is reflected from a closed end is shifted by half a wavelength from one that is reflected by an open end

Question 21

define counterpropagating wave

Answer 21

original and reflected waves interact and lead to standing waves

Question 22

define standing waves

Answer 22

a standing wave is a wave which oscillates in time but whose peak amplitude profile doesn’t move in space

Question 23

define a node

Answer 23

locations on a wave where displacement is 0 at all times

Question 24

define anti-node

Answer 24

locations where the displacement oscillates with maximum amplitude

Question 25

define sound wave

Answer 25

a pressure change wave that is generally caused by a vibration and can propagate in gas, liquid, and solids compression and rarefaction (individual particles oscillate but there is no net displacement of the medium, particles at the peak or trough of the wave experience no force and have max acceleration)

Question 26

define the doppler effect

Answer 26

the frequency of a wave will appear to be increased/decreased if the source or receiver is moving

Question 27

define a "beat"

Answer 27

two waves with different frequencies (for example the original wave and a doppler shifted wave) will create "beats"