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Physics - Y10 + Y11 > Waves - Y10 > Flashcards

Waves - Y10 Flashcards

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1
Q

What are waves?

A

They transfer energy from 1 place to another without transferring any matter

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2
Q

Give an examples of a transverse wave

A
  • Ripples on a water surface
  • EM Waves
  • Wave on a string
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3
Q

Give an examples of a longitudinal wave

A
  • Sound waves
  • Shock waves
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4
Q

What are transverse waves?

A
  • Oscillations are perpendicular (90’) to the direction of the energy transfer
  • Oscillations (vibrations) are up and down
  • Energy transfer is sideways
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5
Q

What are longitudinal waves?

A
  • Oscillations are parallel to the direction of energy transfer
  • Consists of compressions & rarefactions
  • Need a medium to travel in e.g air, solid, liquid
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6
Q

Amplitude

A

The maximum displacement of a point on the wave from its undisturbed point (height)

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7
Q

Wavelength

A

Distance between the same point on 2 adjacent waves

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8
Q

Frequency

A

Number of waves passing a point each second

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9
Q

What does 1 Hz mean?

A

1 wave per second

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10
Q

Period

A

Time (seconds) for one wave to pass a point

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11
Q

How do you find the period?

A

Period(s) = 1/ frequency (Hz)

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12
Q

What is the wave speed?

A

Speed at which energy is being transferred or speed the wave is moving at

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13
Q

Equation for speed (units)

A

v = λ f
wave speed (m/s) = wavelength (m) X frequency (Hz)

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14
Q

What 3 things can happen to a wave? What does this depend on?

A
  • Absorbed by the material (transfers energy to the material’s energy stores)
  • Transmitted (goes through the material, gets refracted and carries on moving)
  • Reflection
    These depend on the wavelength and properties of the materials involved
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15
Q

What is the rule for all reflected waves?

A

Angle of incidence = angle of reflection

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16
Q

What degree is the normal always at in a ray diagram?

A

90’

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17
Q

What is specular reflection?

A
  • Happens on a smooth surface
  • Wave is reflected in a single direction
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18
Q

What is diffuse reflection?

A
  • Happens on a rough surface
  • Reflected rays are scattered in lots of different directions
  • All have different mediums
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18
Q

What are EM waves?

A

Electromagnetic waves are:
* transverse waves
* they transfer energy from a source to an absorber
* They all travel at the same speed through air or a vacumm

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19
Q

How does density affect the speed of a wave?

A

Higher density = slower wave travels through it
Low density = faster wave travels through it

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20
Q

Light travelling from a less dense material, into a more dense material, will bend ________ the normal.

A

towards

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21
Q

What happens when a wave slows down?

Include density

A

When it goes through a high density object, it will bend towards the normal

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22
Q

What happens when a wave speeds up?

Include density

A

When it goes through a low density object, it will bend away the normal

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23
Q

Ray diagrams: What happens if the 2nd material optically denser than the 1st?

A

Refracted ray bends towards normal - angle between refracted ray and normal is smaller than angle of incidence

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24
Q

Ray diagrams: What happens if the 2nd material is less optically dense than the 1st?

A

Angle of refraction is larger than angle of incidence (away from normal)

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25
Q

Electromagnetic spectrum in order
Describe the freq and wavelength

A
  1. Radio waves - Low freq, longer wavelength
  2. Micro Waves
  3. Infra Red
  4. Visible Light - only seen by human eye
  5. Ultra Violet
  6. X-Rays
  7. Gamma Rays - higher freq, shorter wavelength
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26
Q

What speed do EM waves travel at in a vacuum?

A

3 x 10⁸ m/s

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27
Q

How to you find the frequency?

A

Number of waves / time

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28
Q

How many Hz is 1MHz

A

1000000 (6)

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29
Q

2 types of waves formed from earthquake

A

Seismic waves called P and S waves

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30
Q

How do you detect waves from an earthquake

A

seisomemteres

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31
Q

What are P-waves?

A
  • Longitudinal
  • Travel through solids and liquids and gases (fastest in solids)
  • faster than s waves
  • pass through core
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32
Q

What are S waves?

A
  • Transverse
  • Travels only in solids
  • Slower than P waves
  • Travels in curved lines
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33
Q

What is the S wave shadow zone?

A
  • Where no S waves can be detected
  • Because S waves cant pass through a liqiud - tells us Earth has a liquid core
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34
Q

What is the P-wave shadow zone?

A
  • Where waves cant be detected
  • Because P waves travel faster in solids than in liquids - tells us P waves slow down as they enter the liquid outer core - caues them to refrcat
  • They also refract when they leave outer core = outer core is liquid
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35
Q

Normal human ear frequency

A

20 - 20,000 Hz

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36
Q

What is ultrrasound

A

Soundwaves with higher frequency than upper limit of human hearing 20,000Hz

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37
Q

What happens with ultrasound waves and why?

A
  • Get partially reflected at the boundary between 2 diff densities - partial reflection
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38
Q

Equation for distance using ultrasound

A

s = vt
(m) = (m/s) X (s)

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39
Q

How would you find out the depth using the ultrasound distance equation?

A

Substitute then divide by 2 so get depth, otherwise you would get the total + reflected distance

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40
Q

Uses for ultrasound

A
  • Medical imaging eg pre-natal scaaning of a foetus
  • Industrial imaging eg finding flaws in materials/ hidden defects/ problems with a weld
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41
Q

How does ultrasound work in medical imaging?

A
  • Wves can pass through the body but when they reach a boundary between 2 diff media (womb fluid and skin of foetus), some wave is reflected back and detected
  • Exact timing and distribution of these echoes are processed to make a video image
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42
Q

How is ultrasoud used in industrial imaging?

A
  • Used to find flaws in pipes, wood, metal
  • Waves entering a material will usually be reflected from the farside of the material
  • If there is a crack, it would be reflected sooner
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43
Q

What is echo sounding?

A
  • Uses high frequency sound waves
  • Used by boats and submarines to find out the depth of water
  • Or to locate objects in deep water
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44
Q

What are sound waves caused by?

A

Vibrating objects - vib. passes throught the surrounding medium as a sreies of compressions and rarefactions

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45
Q

Where does sound travel faster in?

A

In solids than liquids
In liquids than gases

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46
Q

What happens when a sound wave travels through a solid?

A

Causes particls to vibrate

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47
Q

Can sound travel in space, why?

A

No, mostly a vaccum, no particles to move/vibrate

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48
Q

How do you hear sound, steps?

A
  1. Sound waves reach ear drum, causes it to vibrate
  2. Vibrations -> ossicles (small bones) -> semicircular canals -> cochlea
  3. Cochlea turns vib. to electrical signals -> brain, allow yuo to sense the sound
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49
Q

Where will sound waves be reflected, what does that cause?

A

Refleted by hard flat surfaces = reflected sound waves = echoes

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50
Q

When do sound waves refract? What happens when they enter a dense thing, why?

A

When they enter diff media
Denser material = speed up because wavelength changes, but frequency stays the same, so speed must also change

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51
Q

What are radio waves used for?

A

used to transmit radio and terrestrial TV Signals

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52
Q

What is terrestrial TV?

A

Not satellite or cable TV, received using an aerial

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53
Q

Why are radiowaves used?

A
  • Can travel long distances befroe being absorbed by buildings/trees
  • Longer wavelength radio waves can also spread out between hills (diffraction)
  • Can reflect off a layer of charged particles in the atmosphere (ionosphere) - allows us to send v long distances around the Earth
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54
Q

Uses of microwaves

A

Heating food, communication with satellites in space

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55
Q

Why are microwaves used for heating food?

A
  • Most food contain water molecules
  • Water molecules absorb the energy of microwaves
  • Energy causes temp of food to increase
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56
Q

Why are microwaves used to com. with satellites in space?

A
  • Can pass through Earths atmosphere without being reflected or refracted
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57
Q

Uses of infrared

A
  • Emitted by electrical heaters
  • Cook food in ovens
  • Infrared cameras
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58
Q

Why is infrared used in heaters?

A

Energy of infrared is easily absorbed by the surface of the objects. Makes the room warmer as infrared is absorbed

59
Q

Uses of visible light

A
  • Com. using fibre optics (in telephones and cable TV signals)
60
Q

How do optical fibres work?

A
  1. Transmit pulses of light down fibres and use pulses to carry info
61
Q

Why is visible light used in optical fibres?

A

Short wavelength allows it to carry lots of info

62
Q

Uses of UV

A
  • Energy efficient lightbulbs
  • Suntanning
63
Q

How do energy efficient ligtbulbs work?

A
  1. UV light made in the bulb
  2. UV has a shorter wavelength, carries more energy than visible light
  3. Energy of UV is absorbed by the internal surface of the bulb and is converted to visible light
  4. This requires less energy than a normal light bulb
64
Q

Negatives of UV

A

Premature skin aging, increases risk of skin cancer

65
Q

Uses of gamma and x rays

A
  • Medical imaging
  • Med treatments eg cancer
  • Gamma = detect cancer
    X rays = visualise broken bones
66
Q

Why are gamma and x-rays used in medical imaging?

A

Both rlly penetrative, can easily pass through body tissue

67
Q

How do X-ryas work in MI?

A

Absorbed by bones

68
Q

What do lenses do?

A

Refract light

69
Q

What are convex lenses?

A
  • Bulge outwards
  • Thicker in the middle
  • Produce real and virtual images
  • Causes rays of light to converge at a focal point
70
Q

What are concave lenses?

A
  • Rays of light diverge
  • Always produce virtual images because of light rays appear to come from the nearside focal point
  • Lenses go inwards
71
Q

Sign for convex?

A

↕

72
Q

Sign for cancave?

A

Inward facing arrows

73
Q

2 important facts about parallel rays of light passing through a convex lens

A
  1. Central ray passes through the lens without being refracted because this ray is passing directly along the normal, its passing along the principal axis
  2. All other rays refract and are focused on a point (Principal focus) - F
74
Q

Principal focus

A

Where all other rays focus

74
Q

What is the principal axis?

A

Centre of the lens

75
Q

Focal length

A

Distance from centre of lens to principal focus

76
Q

What is a real image? How is it diff to a virtual

A

Real = rays acc meet
Virtual = they dont, make a dashed line backwards

77
Q

6 feautures an image can be on a ray diagram

A
  • Diminished/Magnified
  • Inverted/ right way up
  • Real/Virtual
78
Q

Object is more than 2 focal lengths from lens

A
  • Image is dimished, inverted,real
79
Q

Object between 1 and 2 focal lengths from lens

A
  • Image is magnified, inverted, real
80
Q

What surface is the best absorbers and emitters of infrared radiaiton?

A

Matt black surfaces

81
Q

What 2 things depend on the temp of the object?

A

Wavelength and intenisty of radiation

82
Q

What length wavelength do v hot objects emit?

A

Shorter

83
Q

What happens to the radiation when temp increases?

A

Intensity of radiaiton
increases

84
Q

What is a perfect black body?

A

Absorbs all the radiation incident on it
* No radiation reflected or transmitted
* Best possible emitter of radiation

85
Q

What happens if an object is warmer than its surroundings?

A
  • Emit more radiation than it absorbs
  • Temp of object decreases
86
Q

What happens if an object is cooler than its surroundings?

A
  • Absorb more radiation than it emits
  • Temp increases
87
Q

What happens if an object is at a constant temp to its surroundings?

A
  • Absorbing rad. at the same rate as it is emitting rad.
88
Q

How does the Earth lose/gain energy?

A

By absorbing or emitting rad

89
Q

How does the Earth’s temp increase?

A
  1. Sun emits short wavelength rad (UV/ visible light)
  2. Travels to eaarth
  3. Some is reflected by clouds
  4. Remaining rad is absorbed by surface of earth
  5. Causes temp to increase
  6. EARTH EMITS INFRARED RAD BACK INTO SPACE
  7. Some energy of infrared is trapped by greenhouse gases
90
Q

Why do very hot objects produce visible light?

A

Because as an object gets hotter, the wavelength becomes shorter

91
Q

Which is warmer? Cloudy nights or clean nights? Why?

A

Cloudy - clouds can reflect infrared back to the Earth and prevent it being radiatied into space

92
Q

What travels in both transverse and longitudinal waves?

A

The wave and not the water or the air

93
Q

RP 8

What is a ripple tank used for?

A

to observe the feautrues of water waves

94
Q

RP 8

Describe a ripple tank

A
  • Shallow tray of water.
  • In the water is a vibrating bar connected to a power pack.
  • When bar vibrates, creates waves
  • A lamp above ripple tank
    Below ripple tank is white paper
95
Q

RP 8

What happens when line shines through the water?

A

It produces an image of the waves on the paper

96
Q

RP 8

What is the easiest way to record waves?

A

Using a mobile phone = you can play back the recording at diff speeds or freeze image

97
Q

RP 8

Method

A
  1. Ruler on paper -> measure distance between one wave and 10 waves further (10 wavelength eg = 0.26m)
  2. Find one wavelength divide by number of waves counted for each wavelength
  3. Calc freq = place timer next to paper and count no of waves passing a point in 10 s then divide by 10
  4. Use v= f lambda
98
Q

How calc freq?

A

no of waves / time

99
Q

RP 8 Waves in a solid

Apparatus

A
  • mass
  • pulley on clamp
  • wooden bridge
  • string
  • vibration generator
  • signal genetator
100
Q

What does the signal generator do?

A

allows us to change freq of vibration of string

101
Q

RP 8 Waves in a solid

What is a standing wave?

A

Wave caused by resonance

102
Q

RP 8 Waves in a solid

Method to measure wave speed of standing wave

A
  1. Measure wavelength using ruler from wooden bridge to vibration generator
  2. Read freq from signal generator
  3. Use v=f Lambda
103
Q

RP 8 Waves in a solid

What happens in you increase the freq in a standing wave?

A
  • More no of half wavelengths
104
Q

How would you calculate wavelength of 3 1/2 wavelengths?

A
  1. Find total distance of the wavelengths by measuring ruler form wooden bridge to vibration generator
  2. Divide that by no of half wavelengths then X2
105
Q

Does the wavespeed of the string depend on freq or wavelength?

A

no, it depends on taughtness of string and mass per cm

106
Q

RP 9 Reflection and refraction

Apparatus

A
  • Ray box
  • lens
  • slit
  • glass box
107
Q

RP 9 Reflection and refraction

Method

A
  1. Take piece of a4 paper and straight straight line down centre with ruler
  2. Use protractor to draw a line at right angles = normal
    3.Place glass block against first line so normal is near centre of block
    4.draw around glass block
    5.turn lights off in room
    6.use ray box to direct ray of light so it hits block at the normal = incident ray
    7.Angle between incident ray and normal = angle of incidence
    8.adjust ray box and change engle of incidence = at a certain angle, we can see ray reflect from surface of the block + transmitted ray leaviing block
    9.Mark path of incident ray and relfected ray + transmitted ray with crosses
    10.Remove block and turn on lights, draw and join trnasmitted ray to centre of block
  3. Protractor and measure angles (incidene and reflection and refraction (between normal and transmitted ray))
  4. Repeat with diff material block
108
Q

Why may we not be able to hear frequencies between 20 - 20,000 Hz

A

may not be able to cause eardrum to vibrate

109
Q

Why does sound travel faster in solids?

A

Particles close togther = vibration can pass more easily between them than gases

110
Q

What also changes when the wavespeed changes as waves pass from 1 medium to another?

A

wavelength eg is wavespeed up, wavelength up

111
Q

What does not change when a wave changes medium?

A

freq cuz they would have to be destroyed/created at the boundary which isnt possible

112
Q

How can we view the features of a sound wave?
Name a prob with this

A
  • connecting a microphone to a cathode ray oscilloscope
  • Represents sound waves as if they were transverse waves which they arent
113
Q

High freq =
low freq =

A

high pitch
low pitch

114
Q

small amplitude
large amplitude

A

quiet
loud

115
Q

What can sound waves only move through and why?

A

A medium eg air or a solid beacuse sound waves move by particles vibrating so they cant pass through a vacuum

116
Q

What do ultrasound only work on?

A

anything not surrounded by bone

117
Q

Why is ultrasound safer than X rays?

A

Doesnt cause mutations and doesnt increase risk of cancer

118
Q

Layers of the earth and their state

A
  1. Inner core (solid)
  2. Outer core(liquid)
  3. Mantle(solid but upper mantle can flow)
  4. Crust (thin solid)
119
Q

How do scientists know the structure of the earth?

A

Earthquakes
* Sudden movement between tectonic plates in crust
* causes seismic waves which carry energy away from earthquake
* these pass through earth and be detected by seismometres in diff countries
* patterns of these waves gives info about interior

120
Q

Why do seismic waves travel in curved paths?

A

due to density changes in the earth

121
Q

How do scientists know that the Earth has a solid inner core?

A

Sometimes faint P waves can be detected in shadow zone = solid inner core

122
Q

What type of spectrum is the EM spectrum?

A
  • continous spectrum
  • cut-off point between one type of wave and other is not always clear
123
Q

When do waves change direction (refract)?

A

when they change speed, moving from 1 medium to another

124
Q

When do wave not refract?

A

when waves enter/leeave medium at right angles to the surface/along normal

125
Q

What is the wavefront?

A

imaginary line that connects all the same points in a set of waves

126
Q

rp 10

What 4 diff surfaces does the Leslie cube have?

A
  • shiny metallic
  • white surface
  • matt black
  • shiny black
127
Q

rp 10

Method

A
  1. Fill Leslie’s cube with hot water
  2. Point an infrared detector at each of the 4 surfaces and record amount of infrared emitted
  3. Same distance between the 2 = makes measurements repeatable
128
Q

rp 10

Leslie Cube results

A
  • Matt black surface releases the most infrared emission
  • then shiny black
  • then white
  • least = shiny metallic
129
Q

rp 10 - leslie

Method but without an infrared detector

A
  • Use a thermometer with the bulb painted black
  • however, resolution (smallest change that can be detected) of thermometer is less than infrared detector
  • infrared more likely to detect a diff
130
Q

rp 10

How would you measure the absorbence of infrared aparatus

A
  • 2 Metal plate - 1 painted shiny metallic and one matt black paint
  • On the other side of each plate, use vaseline to attach drawing pin
  • Infrared heater between 2 plates
131
Q

Method: How would you measure the absorbence of infrared aparatus

A
  1. Swithc on heater and timer
  2. temp of metal plates increases as they absorb infrared
  3. record time it takes for vaseline to melt and drawing pins to fall off
  4. we see that the drawing pin falls of the matt black plate first as they absorb more infrared
  5. matt black better at absorbing and emitting infrared
  6. shiny metallic reflects infrared
132
Q

What happens when EM waves are generated or absorbed?

A

changes take place in atoms or in the nuclei of atoms

133
Q

What happens when we heat atoms? What causes it to generate an EM wave

A
  • electrons move from energy level to a higher one (outwards)
  • When it returns to its original energy level it generates em wave (light)
134
Q

How can a change in the nucleus produce em waves?

A
  • gamma rays can be emitted from nucleus from radioactive atoms
  • when emitted, nucleus has less energy than start
135
Q

How are radiowaves produced?

A
  • produced when electrons oscillate in electrical ciruits
  • these radiowaves can be absorbed eg by electrical circuit in an aerial
  • when this happens, electrons in circuit oscillate
  • creates an ac w/ same freq as radiowaves
136
Q

what happens when light waves move from air to glass?

A

slow down as glass is denser, bend towards normal

137
Q

When is the only time a convex lens produces a virtual image

A

used as a magnifying glass

138
Q

If you made light go through a green filter, what colour would you see and why?

A

Green because all the other colours are absorbed apart from green which is transmitted

139
Q

Why do white objects appear white?

A

Because the reflect all the wavelength of visible light equally

140
Q

Why do black objects appear black?

A

They absorb all the wavelength of visible light

141
Q

Why do red objects appear red?

A

red object absorbs all the colour of white light except red which is reflected

142
Q

What colour would appear if with red filter and green object?

A

black as it reflecting no light

143
Q

What happens to X rays whent hey enter a bone?

A

They are absorbed

144
Q

State one use of infrared and microwaves

A

infrared = fibre optics
microwaves = satelltie com.

Physics - Y10 + Y11 (7 decks)

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