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P4- WAVES > 4.5- STATIONARY AND PROGRESSIVE WAVES > Flashcards

4.5- STATIONARY AND PROGRESSIVE WAVES Flashcards

1
Q

When a guitar string is plucked what is the sound produced dependent on?

A

way in which string vibrates

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2
Q

What happens if a string on a guitar is plucked gently at its centre?

A

stationary wave of constant frequency set up on string

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3
Q

When a string on a guitar is plucked at the centre and a stationary wave of constant frequency is set up, what is the frequency of sound produced like?

A

sound produced has constant frequency

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4
Q

What happens if a guitar string is plucked harshly?

A

string vibrates in more complicated way + not produced contains other frequencies, as well as frequency produced when plucked gently

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5
Q

When is a stationary wave formed?

A

when two progressive waves pass through each other

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6
Q

How can a stationary wave be achieved on a string in tension?

A

by fixing both ends + making middle part vibrate, so progressive waves travel towards each end, reflect at ends, + then pass through each other

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7
Q

What is the simplest stationary wave pattern on a string called?

A

first harmonic of string

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8
Q

What is the first harmonic of a string sometimes referred to as the strings —?

A

fundamental mode of vibration

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9
Q

What does the first harmonic of a string consist of?

A

single loop that has a node at either end

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10
Q

What is a node?

A

point of no displacement

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11
Q

On the first harmonic of a string, where does the string vibrate with maximum amplitude?

A

midway between the nodes

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12
Q

What is the point of the first harmonic of a string where there is maximum amplitude referred to as?

A

antinode

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13
Q

As there are antinodes at the midway of the nodes, how does the string vibrate?

A

from side to side repeatedly

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14
Q

For the first harmonic pattern to occur, what must the distance between the nodes at either end be like?

A

must be equal to one half-wavelength of waves on string

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15
Q

Equation for distance between adjacent nodes?

A

distance between adjacent nodes = 1/2λ

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16
Q

What happens if the frequency of the waves sent along the rope from either end is raised steadily, when the pattern is of a first harmonic?

A

pattern disappears and new pattern observed with two equal loops along rope

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17
Q

What is the new pattern (second harmonic) observed when the frequency is increased like?

A

has node at centre + at either end

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18
Q

When is the new pattern observed when frequency is increased formed?

A

when frequency twice as high, corresponding to half the previous wavelength

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19
Q

What is the distance from one node to the next equal to in the second harmonic?

A

equal to have a wavelength

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20
Q

If the distance from one to the next is equal to half a wavelength in the second harmonic, what is the length of the rope equal to?

A

equal to one full wavelength

21
Q

What do stationary waves that vibrate freely not do?

A

stationary waves that vibrate freely do not transfer energy to their surroundings

22
Q

What is the amplitude of vibration at the nodes?

A

zero

23
Q

As the amplitude of vibration is zero at the nodes, what does this mean?

A

no energy at the nodes

24
Q

Where is the amplitude of vibration a maximum?

A

at the antinodes

25
Q

As the amplitude of vibration is a maximum at the antinodes, what does this mean?

A

maximum energy at antinodes

26
Q

Why is no energy transferred in a vibrating stationary wave pattern?

A

because nodes + antinodes are at fixed positions

27
Q

What happens when two progressive waves are in phase?

A

reinforce each other to produce large wave

28
Q

What happens a quarter of cycle when two progressive waves are passing through each other?

A

two waves have each moved one-quarter of a wavelength in opposite directions- now in antiphase so cancel each other

29
Q

What happens after a further quarter cycle (now half) when two progressive waves are passing through each other?

A

two waves back in phase. resultant again a large wave, except reversed

30
Q

Are the points where there is no displacement fixed in position throughout? (explanation of stationary waves)

A

yes

31
Q

What happens between the points of no displacement?

A

stationary wave oscillates between nodes

32
Q

How does the amplitude of a vibrating particle in a stationary wave pattern vary with position?

A

from zero at node to maximum amplitude at antinode

33
Q

When is the phase difference between two vibrating particles in a stationary wave zero?

A

if two particles between adjacent nodes or separated by even number of nodes

34
Q

What is the phase difference between two vibrating particles in a stationary wave 180° (= π radians)?

A

if two particles separated by odd number of nodes

35
Q

What is the frequency like in stationary waves?

A

all particles except those at nodes vibrate at same frequency

36
Q

What is the frequency like in progressive waves?

A

all particles vibrate at same frequency

37
Q

What is the amplitude like in a stationary wave?

A

amplitude varies from zero at nodes to maximum at nodes

38
Q

What is the amplitude like in a progressive wave?

A

amplitude same for all particles

39
Q

What is the phase difference between two particles in a stationary wave like?

A

equal to mπ

m- number of nodes between two particles

40
Q

What is the phase difference between two particles in a progressive wave?

A

equal to 2πd/λ
d= distance apart
λ= wavelength

41
Q

What is sound in an air-filled tube or pipe like?

A

sound resonates at certain frequencies

42
Q

What happens to resonant frequencies in a pipe closed at one end?

A

resonant frequencies occur when there is an antinode at open end + node at other end

43
Q

Where are microwaves from a transmitter directed normally?

A

at a metal plate

44
Q

What does the metal plate do when a microwave from a transmitter is directed at it?

A

reflects microwaves back towards transmitter

45
Q

When a detector is moved along the line between a microwave transmitter and the metal plate, when is the detector signal found to be zero (or at a minimum?

A

at equally spaced positions along the line

46
Q

What do the reflected waves and waves from the transmitter form? (using microwaves)

A

stationary wave pattern

47
Q

What is the positions where no signal (or minimum) is detected? (using microwaves)

A

where nodes occur

48
Q

How are the nodes spaced? (using microwaves)

A

at intervals of half a wavelength

P4- WAVES (7 decks)

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