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Waves 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
How do we reduce the error with the cymbals/timer experiment?
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
26
How does hearing work?
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
27
Normal human hearing frequency range
20Hz - 20,000Hz
28
What controls the human hearing range?
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
29
What happens if waves go from one medium to another?
Their speed can change Ie speed travels faster in solids because particles are closer than gases so vibrations pass easier between them
30
Vibrations
Longitudinal sound waves causing air particles to move back and forth sideways Or parallel to direction of travel Passed along and causes sound
31
According to the wave equation, how do waves changing medium affect the wave speed?
If the wave passes from one medium to another it’s speed changes Thus its wavelength changes THE FREQUENCY DOES NOT CHANGE
32
Why does the frequency not change if a wave changes medium?
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
How can we view features of sound waves?
Connect a microphone to a cathode ray oscilloscope
34
Disadv of cathode ray oscilloscope
Represents sound waves as if they were transverse waves But they are longitudinal So dont get confused
35
What determines pitch of sound?
THE FREQUENCY HIGH FREQUENCY so more waves = HIGH PITCH LOW FREQUENCY so less waves = LOW PITCH
36
What determines the volume of a wave?
AMPLITUDE SMALL AMPLITUDE so short and fat wave = QUIET LARGE AMPLITUDE so long and thin wave = LOUD
37
Why can’t sound waves travel through a vacuum
Only move if the particles are vibrating side to side between each other Thus no particles = no sound
38
How are sound waves reflected?
Reflected sound wave = Echo
39
Ultrasound
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
What do ultrasound waves do at the boundary between different densities?
Partially reflect right back
41
Uses of ultrasounds
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
Why is ultrasound safer than x rays?
Doesn’t cause mutations so no risk of cancer
43
How can we determined distance using ultrasound
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
Interior of the Earth and its state
Crust, thin layer = solid \/\/\/\/\/\/\/ Mantle = solid but can flow slowly \/\/\/\/\/\/\/ Outer core = liquid \/\/\/\/\/\/\/ Inner core = solid
45
How do scientists know the interior of the Earth if we have only dug a bit of the crust?
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
Types of seismic waves
P waves S waves
47
P waves properties
Longitudinal Pass through solids and liquids, but like all longitudinals not gases Faster than S waves
48
S waves properties
Transverse waves Only through solids Travels slower than P waves
49
How to remember S waves properties?
Everything with S tranSverSe wave Only Solids Slower Speed than P waves
50
S wave shadow zone
Zone where there are no S waves That is because they can’t pass through liquid
51
What does the S wave shadow zone show scientists?
There must be a liquid core for the Earth because S waves can’t go through there
52
S waves patterns through Earth
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
P wave patterns
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
What causes p wave shadow zone and what does it show?
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
What shows the inner core is a solid?
Faint P waves In shadow P zones
56
Electromagnet wave
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
Visible light through a prism
Splits to spectrum of colours
58
Colours in visible light
Red Orange Yellow Green Blue Indigo Violet ROY G BIV
59
Frequency in colours
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
Wavelength from colours in visible light
DECREASE as you go from RED ———> VIOLET so red has longer wavelength than violet because it decreases as you go down
61
How to remember the changes in colour spectrum?
RLLL Red = low frequency = long wavelength = less energy So opposite for the other side
62
Electromagnetic spectrum
🎶Radio waves Microwaves Infrared radiation Visible light Ultraviolet X rays Gamma rays 🎵
63
How does frequency change in the electromagnetic spectrum?
INCREASE from RADIO ———> GAMMA RAYS So radio waves have less waves than gamma rays in one second because it increases
64
How does wavelength change in electromagnetic spectrum?
DECREASE from RADIO ———> GAMMA RAYS so radio waves are longer/stretched out sideways than gamma rays because the wavelength decreases
65
How to remember properties of electromagnetic spectrum?
Just like colour spectrum RLLL Radio = Low frequency = Long wavelength = less energy
66
What is the part of electromagnetic spectrum visible to human eye?
Visible light the ONLYYYY
67
What type of spectrum is electromagnetic and why?
Continuos The cut off point between one type and the other is not always clear
68
Can electromagnetic waves travel in a vacuum?
Yes because they are transverse waves which have the possibility to
69
How do electromagnetic waves travel in a vacuum?
All at the same speed
70
What speed do electromagnetic waves travel in a vacuum?
300 000 000m/s Or 3 x 10^8 m/s
71
What happens to electromagnets based on their wavelengths?
What material transmits, reflects or absorbs them
72
Example of how microwaves act in terms of reflection, absorption or transmission
Microwaves are absorbed by food which cooks them But reflected by metals
73
Examples of how visible light waves act in terms of different surfaces
Matt black = absorbed Shiny metallic = reflected
74
What happens when electromagnetic waves are generated or absorbed?
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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