Waves

Question 1

what is a transverse wave

Answer 1

when the displacement is at right angles to the direction of the wave

Question 2

what is a longitudinal wave

Answer 2

when the displacement is parallel to the direction of the wave

Question 3

define amplitude

Answer 3

this is the distance from equilibrium to the crest or trough of the wave

Question 4

define wavelength

Answer 4

λ, this is the distance between two consecutive, corresponding points

Question 5

define period

Answer 5

the time for one whole wave to pass a point (s), T

Question 6

define frequency

Answer 6

how many full waves pass a point every second, measured in Hertz, Hz. f=1/T

Question 7

what is the wave equation

Answer 7

v=fλ

Question 8

define the doppler effect

Answer 8

the doppler effect is the change in the perceived frequency caused by the motion of the wave source

Question 9

true or false: for a stationary source, the wavelength is the same in all directions

Answer 9

true

Question 10

true or false: even for a moving source the wavelength is the same in all directions

Answer 10

false

Question 11

when a source is approaching, the perceived wavelength is _____

Answer 11

shorter

Question 12

when a source is approaching, the wave speed is ______

Answer 12

the same

Question 13

when a source is approaching, the perceived frequency is ____

Answer 13

higher

Question 14

when the source is moving away, the perceived wavelength is ____

Answer 14

longer

Question 15

when a source is moving away, the wave speed is __

Answer 15

the same

Question 16

when a source is moving away, the perceived frequency is ____

Answer 16

lower

Question 17

what does Vw stand for in the doppler equation

Answer 17

the speed of a wave in a particular medium, often the speed of sound

Question 18

what does Vs stand for in the doppler equation

Answer 18

the speed of the source

Question 19

what does f’ stand for in the doppler equation

Answer 19

the apparent frequency

Question 20

in the doppler equation, when would you use the + or the - in the denominator

Answer 20

• if the source is moving towards the observer, + if the source is moving away from the observer

Question 21

how is a standing wave formed

Answer 21

when you wiggle the end of a spring, a wave travels down the spring, reflects off a fixed end inverted and comes back. if you send a series of waves with the same frequency and amplitude, they can interfere with the reflected waves to set up a standing wave

Question 22

what does a travelling wave do

Answer 22

transfer energy

Question 23

true or false: in a travelling wave, all points have the same amplitude

Answer 23

true

Question 24

define fundamental frequency

Answer 24

the lowest possible frequency standing wave is called the 1st harmonic

Question 25

how many wavelengths long is the first harmonic

Answer 25

1/2λ

Question 26

define a node

Answer 26

nodes are points of zero amplitude

Question 27

define an antinode

Answer 27

points of maximum amplitude

Question 28

what are harmonics

Answer 28

there are only certain frequencies that a standing wave can have, and these are called the harmonics

Question 29

harmonics are always ____ of the fundamental

Answer 29

multiples

Question 30

The distance between two adjacent nodes or antinodes is always

Answer 30

half a wavelength

Question 31

in the diagram of the fundamental harmonics, which points represent nodes and antinodes

Answer 31

antinodes are shown by the highest point above the equilibrium position, nodes sit on the equilibrium position

Question 32

what is the length of the 1st harmonic

Answer 32

1/2λ

Question 33

what is the wavelength of the 1st harmonic

Answer 33

2 x L

Question 34

what is the frequency of the 1st harmonic

Answer 34

f1

Question 35

what is the length of the 2nd harmonic

Answer 35

λ

Question 36

what is the wavelength of the second harmonic

Answer 36

1 x λ

Question 37

what is the frequency of the 2nd harmonic

Answer 37

2 x f1

Question 38

what is the length of the 3rd harmonic

Answer 38

3/2 λ

Question 39

what is the wavelength of the 3rd harmonic

Answer 39

2/3 x L

Question 40

what is the frequency of the 3rd harmonic

Answer 40

3 x f1

Question 41

describe how air forms nodes and antinodes in an open pipe

Answer 41

air bunches up in the middle of the pipe to form a node. there are antinodes at either end of the pipe where the air is much more free

Question 42

describe how air forms nodes and antinodes in a closed pipe (where one end is closed)

Answer 42

there is a node at the closed end and an antinode at the open end

Question 43

how are beats formed

Answer 43

when two sources emit waves of similar frequency the resultant wave has the frequency of the average between two frequencies, and its amplitude fluctuates with the frequency which equals the distance between the two

Question 44

how do you calculate the frequency of the beats

Answer 44

If1-f2I

Question 45

define constructive interference

Answer 45

when two waves arrive in phase (pd=nλ)

Question 46

define destructive interference

Answer 46

when two waves arrive out of phase (pd=n-1/2λ)

Question 47

what is L of a diffraction grating

Answer 47

the distance between the grating and the screen

Question 48

what is x of a diffraction grating

Answer 48

distance between two neighbouring bright fringes

Question 49

what is theta of a diffraction grating

Answer 49

spectral angle

Question 50

what is d of a diffraction grating

Answer 50

slit seperation

Question 51

nm=10^?

Answer 51

-9

Question 52

mm=10^?

Answer 52

-3

Question 53

micrometre=10^?

Answer 53

-6

Question 54

what colour has the shortest wavelength

Answer 54

purple

Question 55

which colour has the longest wavelength

Answer 55

red

Question 56

what does capital N represent

Answer 56

the number of lines per metre

Question 57

how do you work out d, the distance between lines, if you are given the number of lines per metre N

Answer 57

1/N = d or 1/d = N

Question 58

what do dark areas on a screen from a diffraction grating represent

Answer 58

areas where light from different slits interferes destructively, waves arrive out of phase and cancel each other

Question 59

the _____ the wavelength the higher the path difference

Answer 59

longer

Question 60

the inference pattern on the screen depends on colour, and the particular ____ of that colour

Answer 60

wavelength

Question 61

for a longer λ the bright spot on the screen will be ________ from the centre

Answer 61

further away

Question 62

if λ goes up, the ___ goes up in nλ=dsintheta

Answer 62

angle, theta

Question 63

how is a standing wave formed

Answer 63

when there is an incoming travelling wave and a reflected wave travelling in the opposite direction

Question 64

when a wave is reflected, it changes ___

Answer 64

phase

Question 65

when incoming and reflected waves add together the increase or decrease periodically of the amplitude of the standing wave depends on ___ ____ ____ of the two waves eg?

Answer 65

the phase difference. eg: two waves of the same phase add together to create a wave of the same phase but double the amplitude, while waves that are out of phase (antiphase) cancel each other out