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Physics > Waves > Flashcards

Waves Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

Wave

A

A way in which energy is transferred from one place to another
Eg water ripples transfers kinetic energy

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2
Q

2 categories of waves

A

Transverse
Longitudinal

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3
Q

What type of wave is ripples on water?

A

Transverse

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4
Q

What defines a transverse wave?

A

If the oscillations are perpendicular to the direction of energy transfer

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5
Q

Transverse waves appearance

A

Oscillations (up and down)
Move in the direction the energy is being transferred

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6
Q

What defines longitudinal waves?

A

The oscillations are parallel to the direction of energy transfer

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7
Q

Longitudinal waves appearance

A

Upwards lines
Compressions = where particles are close together
Refractions = where they are spaced out
Oscillations move sideways

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8
Q

Transverse vs longitudinal waves

A

ALL types of Longitudinal waves require a medium to travel in like air, a solid or liquid
However not all transverse waves do

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9
Q

Examples of transverse waves

A

Light
Ripples on water

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10
Q

Examples of longitudinal waves

A

Sound

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11
Q

Do waves transfer matter?

A

NO JUST ENERGY!!!
so they do not move air particles if they travel through air
Or move water particles in water
They move on their OWN!!!!

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12
Q

How do transverse waves not transfer matter?

A

Because when the wave passes through, the particles just oscillate up and down not travelling through the medium
Because the oscillations perpendicular to the direction of energy transfer

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13
Q

How to longitudinal waves not transfer matter?

A

Because when the wave passes through, the particles just oscillate from side to side not travelling through the medium
Because the oscillations are parallel to direction of energy transfer

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14
Q

Amplitude

A

Maximum displacement of a point on a wave away from its undisturbed position
Aka the peak of the wave to the line

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15
Q

Wavelength

A

Distance from one point on one wave to the equivalent point on adjacent wave
This could be anywhere

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16
Q

How to measure longitudinal wavelength?

A

One compression to next compression
One refraction (not compression) to the next

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17
Q

Frequency

A

Number of waves passing a point each second
1 Hz = 1 wave per second
5 Hz = 5 waves per second

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18
Q

Frequency unit

A

Hertz Hz

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19
Q

Period

A

Time (in s) for one wave to pass a point

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20
Q

Period equation

A

1
———————
Frequency (Hz)

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21
Q

Wave speed

A

The speed at which the wave travels through the medium
And thus transfers energy

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22
Q

Wave equation

A

Wave speed (m/s) = frequency (Hz) x wavelength (m)

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23
Q

How can we find the speed at which a sound wave travels?

A

2 people stood a large distance apart
Person 1 clashes symbols to make a sound
Person 2 starts timing they see this happen using timer then stops when they hear it
Calculate speed = distance they stood apart/ time taken

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24
Q

What is the problem with using the cymbals/timer method to calculate wave speed?

A

People have different reaction times, it may take a different amount of time to press the timer depending on person
Time taken to see the person clash cymbals and hear it is incredibly short

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25
Q

How do we reduce the error with the cymbals/timer experiment?

A

Have multiple observers also using a timer
Take all these results, discard anomalies then calc mean

If the time is too short, increase the distance between both people
So longer distance = longer time to hear it so you can press it at the correct times

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26
Q

How does hearing work?

A

The sound waves hit the boundaries between 2 materials:
They are funnelled into the ear from the air
And hit the eardrum (thin membrane, solid)
Sound waves causes ear drum to vibrate
Causes sensation of sound for us

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27
Q

Normal human hearing frequency range

A

20Hz - 20,000Hz

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28
Q

What controls the human hearing range?

A

The frequency
Because the sound waves in air can trigger vibrations in solids but only for certain frequencies
Outside of that may not make eardrum vibrate

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29
Q

What happens if waves go from one medium to another?

A

Their speed can change
Ie speed travels faster in solids because particles are closer than gases so vibrations pass easier between them

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30
Q

Vibrations

A

Longitudinal sound waves causing air particles to move back and forth sideways
Or parallel to direction of travel
Passed along and causes sound

31
Q

According to the wave equation, how do waves changing medium affect the wave speed?

A

If the wave passes from one medium to another it’s speed changes
Thus its wavelength changes
THE FREQUENCY DOES NOT CHANGE

32
Q

Why does the frequency not change if a wave changes medium?

A

That would mean more or less waves pass a point in a specific second
Therefore they would have to be created at the boundary which isn’t possible

33
Q

How can we view features of sound waves?

A

Connect a microphone to a cathode ray oscilloscope

34
Q

Disadv of cathode ray oscilloscope

A

Represents sound waves as if they were transverse waves
But they are longitudinal
So dont get confused

35
Q

What determines pitch of sound?

A

THE FREQUENCY
HIGH FREQUENCY so more waves = HIGH PITCH
LOW FREQUENCY so less waves = LOW PITCH

36
Q

What determines the volume of a wave?

A

AMPLITUDE
SMALL AMPLITUDE so short and fat wave = QUIET
LARGE AMPLITUDE so long and thin wave = LOUD

37
Q

Why can’t sound waves travel through a vacuum

A

Only move if the particles are vibrating side to side between each other
Thus no particles = no sound

38
Q

How are sound waves reflected?

A

Reflected sound wave = Echo

39
Q

Ultrasound

A

Sound waves with frequency high than upper limit of human hearing
So over 20,000
Pitch of waves depend on frequency therefore it’s very high pitched

40
Q

What do ultrasound waves do at the boundary between different densities?

A

Partially reflect right back

41
Q

Uses of ultrasounds

A

We can see the time it takes for the ultrasound to leave probe, bounce/ reflect off material and detected by probe, we can calc it’s distance away
And produce images eg for internal organs not surrounded by bone
Or detect defects in materials
Or distance from seabed in a ship

42
Q

Why is ultrasound safer than x rays?

A

Doesn’t cause mutations so no risk of cancer

43
Q

How can we determined distance using ultrasound

A

Distance (m) = speed (m/s) x time (s)
For total distance travelled, ie for it to be emitted then reflected up again
Therefore divide this by 2 solely for distance for emitted ultrasound

44
Q

Interior of the Earth and its state

A

Crust, thin layer = solid
\/\/\/\/\/\/\/
Mantle = solid but can flow slowly
\/\/\/\/\/\/\/
Outer core = liquid
\/\/\/\/\/\/\/
Inner core = solid

45
Q

How do scientists know the interior of the Earth if we have only dug a bit of the crust?

A

Using earthquakes
Movements between tectonic plates cause seismic waves
Carrying energy away from earthquake
Pass through Earth and detected by seismometers in different countries
Patterns of these waves give info on the interior of Earth

46
Q

Types of seismic waves

A

P waves
S waves

47
Q

P waves properties

A

Longitudinal
Pass through solids and liquids, but like all longitudinals not gases
Faster than S waves

48
Q

S waves properties

A

Transverse waves
Only through solids
Travels slower than P waves

49
Q

How to remember S waves properties?

A

Everything with S
tranSverSe wave
Only Solids
Slower Speed than P waves

50
Q

S wave shadow zone

A

Zone where there are no S waves
That is because they can’t pass through liquid

51
Q

What does the S wave shadow zone show scientists?

A

There must be a liquid core for the Earth because S waves can’t go through there

52
Q

S waves patterns through Earth

A

Go through the mantle from where the earthquake was
But curve around the outer liquid core as they can’t pass through there
Creating S wave shadow zone

53
Q

P wave patterns

A

Go through the mantle like S waves
But change direction and curve through the outer and inner core so they are through the middle
But leave areas where there are no P waves
= P wave shadow zone

54
Q

What causes p wave shadow zone and what does it show?

A

P waves travel faster in solids than liquids
Because they refract when travelling through solid mantle, to the outer core
Then refract again when leaving

55
Q

What shows the inner core is a solid?

A

Faint P waves In shadow P zones

56
Q

Electromagnet wave

A

Transverse waves
That transfer energy from the source to what’s absorbing it (absorber)
Eg microwaves transfer energy from source (oven) to absorber (food)

57
Q

Visible light through a prism

A

Splits to spectrum of colours

58
Q

Colours in visible light

A

Red
Orange
Yellow
Green
Blue
Indigo
Violet
ROY G BIV

59
Q

Frequency in colours

A

INCREASE as you go from RED ———> VIOLET
So red and orange have fewer waves per second and violet has more because it gets BIGGER as you go down

60
Q

Wavelength from colours in visible light

A

DECREASE as you go from RED ———> VIOLET
so red has longer wavelength than violet because it decreases as you go down

61
Q

How to remember the changes in colour spectrum?

A

RLLL
Red = low frequency = long wavelength = less energy
So opposite for the other side

62
Q

Electromagnetic spectrum

A

🎶Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet
X rays
Gamma rays 🎵

63
Q

How does frequency change in the electromagnetic spectrum?

A

INCREASE from RADIO ———> GAMMA RAYS
So radio waves have less waves than gamma rays in one second because it increases

64
Q

How does wavelength change in electromagnetic spectrum?

A

DECREASE from RADIO ———> GAMMA RAYS
so radio waves are longer/stretched out sideways than gamma rays because the wavelength decreases

65
Q

How to remember properties of electromagnetic spectrum?

A

Just like colour spectrum
RLLL
Radio = Low frequency = Long wavelength = less energy

66
Q

What is the part of electromagnetic spectrum visible to human eye?

A

Visible light the ONLYYYY

67
Q

What type of spectrum is electromagnetic and why?

A

Continuos
The cut off point between one type and the other is not always clear

68
Q

Can electromagnetic waves travel in a vacuum?

A

Yes because they are transverse waves which have the possibility to

69
Q

How do electromagnetic waves travel in a vacuum?

A

All at the same speed

70
Q

What speed do electromagnetic waves travel in a vacuum?

A

300 000 000m/s
Or 3 x 10^8 m/s

71
Q

What happens to electromagnets based on their wavelengths?

A

What material transmits, reflects or absorbs them

72
Q

Example of how microwaves act in terms of reflection, absorption or transmission

A

Microwaves are absorbed by food which cooks them
But reflected by metals

73
Q

Examples of how visible light waves act in terms of different surfaces

A

Matt black = absorbed
Shiny metallic = reflected

74
Q

What happens when electromagnetic waves are generated or absorbed?

A

Changes take place in atoms
Because in an atom, the electron moves up an energy level
It returns to its original one by generating an electromagnetic wave
Or
If a radioactive atom decays and gives off gamma ray
So it has less energy

Physics (44 decks)

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