Topic 6 - Waves Flashcards

1
Q

What is a wave?

A

A wave is a transfer of energy from one point to another via a vibration without the transfer of matter.

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2
Q

What is a Transverse wave?

A

A wave where the vibration/oscillation is at a right angle to the direction of the wave.

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3
Q

Examples of Transverse waves

A

waves on strings
waves on water
EM waves
secondary seismic waves

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4
Q

What is a Longitudinal wave?

A

The vibration/oscillation is along the direction of travel of the wave. All types of Longitudinal waves need a substance to travel in.

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5
Q

Examples of Longitudinal waves

A

sound wavesprimary seismic wavesslinky

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6
Q

What is an Amplitude?

A

The maximum displacement from the rest position. Measured in metres. The larger the amplitude, the larger/more intense the wave is.

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7
Q

What is wave length?

A

λ (lambda); The length of a whole wave, or the distance between two consecutive peaks or troughs. Measured in metres.

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8
Q

What is frequency?

A

Number of waves passing a point per second. Measure in Hertz (Hz).

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9
Q

Frequency Equation

A

f = 1/T

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10
Q

What is a Time Period?

A

The time taken for one complete wave to pass a point. Measured in seconds.

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11
Q

Time Period Equation

A

T = 1/f

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12
Q

Wave Speed Equation

A

v = fλ

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13
Q

Speed of Water Waves => Required Practical - aim

A

Investigate the relationship between the depth of water and the speed of a wave.

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14
Q

Speed of Water Waves => Required Practical - method

A
  1. Measure the length of the base of the tray with a ruler.2. Put water in the tray to a depth of 0.5cm.3. Lift the tray vertically at one end by 5cm.4. Release the tray and start the stop clock when the wave hits the end of the tray that was dropped.5. Time how long it takes the wave to travel 3 lengths of the tray.6. Repeat 3 more times.7. Repeat steps 3-5 for water depths of, 1cm, 1.5cm, and 2cm.
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15
Q

Speed of Water Waves => Required Practical - variables

A

Independent - depth of waterDependent - time for 3 lengthsControl - size of tray, amount of lengths, heigh the tray is dropped from

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16
Q

Speed of Water Waves => Required Practical - conclusion

A

The deeper the depth of water, the faster the speed of the wave.

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17
Q

What 3 things can waves do when they encounter a surface?

A

reflecttransmit (pass through)be absorbed (material takes in energy of wave)

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18
Q

What are the 2 types of reflection?

A

SpecularDiffuse

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19
Q

What can images be characterised by? (5)

A

Real or VirtualSize relative to objectInverted or UprightPosition relative to object and mirror/lensLateral inversion

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20
Q

What is refraction?

A

When light enters another substance and changes its direction.

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21
Q

Refraction => Required Practical - aim

A

Investigate the direction of refracted rays on a prism.

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22
Q

Refraction => Required Practical - method

A
  1. Use a ray box to shine a thin beam of light through perspex.2. With a pencil and a ruler note down where the light rays are on both sides of the perspex.3. Remove the perspex and draw in the refracted ray.4. Measure the angles of incidence and refraction for air to perspex, and perspex to air.
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23
Q

Refraction => Required Practical - conclusion (air to perspex)

A

When light travelled from air to perspex, the angle of refraction is always less than the angle of incidence.

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24
Q

Refraction => Required Practical - conclusion (perspex to air)

A

When a light ray travels from perspex to air, the angle of refraction is always larger than the angle of incidence in perspex, except when the light ray bits the perspex exactly on the normal.

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25
Q

Speed of Light in a vacuum and in air

A

300 000 000 m/s

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26
Q

What happens when light slows down when entering a transparent material?

A

The refracted ray moves closer to the normal. The wave length also decreases compared to what it was when the wave was in air.

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27
Q

What is an electromagnetic wave?

A

Transverse waves that transfer energy from the source of the waves to an absorber

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28
Q

What is the EM waves spectrum?

A

A continuous spectrum of all the possible wavelengths of electromagnetic waves.

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29
Q

How many groups are EM waves put into, and based off what?

A
  • 7 groups- according to wavelength or frequency
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30
Q

What are the 7 groups on the EM spectrum?

A
  • Radiowaves
  • Microwaves
  • Infared
  • Visible light
  • Ultra Violet
  • X-rays
  • Gamma rays
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31
Q

What properties do each end of the spectrum have?

A
  • Radio waves have a low frequency and a large wavelength
  • Gamma rays have a high frequency and a small wave length
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32
Q

What 3 properties do all EM waves share?

A
  • travel at same speed in a vacuum (300 000 000 m/s)
  • transfer energy from a source to an absorber
  • they are transverse
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33
Q

What are Gamma Rays?

A

High energy electromagnetic waves which come from the changes in the nuclei of atoms.

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34
Q

How do radio waves work? (steps)

A

NAME?

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35
Q

Long wave radio - properties

A
  • 1-10km
  • can be transmitted halfway round the world as long wavelengths diffract (bend) around the earths surface
  • diffraction makes it possible for radio signals to be received even if the receiver isn’t in the line of sight of the transmitter
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36
Q

Short wave radio - properties

A
  • 10-100m
  • don’t diffract around earths surface
  • reflected between the Earth and the ionosphere (an electrically charged layer in the earths upper atmosphere)
  • bluetooth uses short wave radio waves to send data over short distances without wires
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37
Q

Medium wave radio - properties

A

NAME?

38
Q

TV signals and FM radio

A
  • short wavelengths (10cm - 10m)
  • to get reception you must be in direct sight of the transmitter
  • the signal doesn’t bend around anything
39
Q

Main 2 uses Microwaves

A

NAME?

40
Q

How do satellite communications use microwaves?

A
  • They use microwaves for satellite communications, as certain wavelengths can easily pass through the earths atmosphere with minimal reflection, refraction, diffraction, or absorption, meaning they can reach satellites
  • The signal from a transmitter is transmitted into space, where satellites receiver picks it up. The satellite transmits the signal back to earth in a different direction, where it’s received by a satellite receiver on the ground. Slight time delay due to long distance travelled.
41
Q

How does cooking use microwaves?

A
  • microwave ovens have wavelengths which allows them to be absorbed by water molecules in food
  • microwaves penetrate a few centimetres into the food before being absorbed and transferring the energy they are carrying to the thermal energy stores of the water molecules in the food causing the water to heat up => water molecules transfer this energy to the rest of the molecules in the food, which quickly cooks it
42
Q

How do Infared Cameras use Infared Radiation?

A

NAME?

43
Q

How does cooking use Infared Radiation?

A

NAME?

44
Q

How do Electric Heaters use Infared Radiation?

A
  • contain a large piece of wire that heats up when a current flows through it => wire emits lots of IR Radiation, this is then absorbed by objects and the air in the room
  • energy is transferred by the IR waves to thermal energy stores of the objects, causing their temp to rise
45
Q

What are fibre optic cables, and how do they work?

A
  • thin glass or plastic fibres that can carry data (e.g. from telephones or computers)- Pulses of visible light used because when light hits walls of fibres, its’s reflected back into the fibre. This means the light is bounced back and forth until it reaches the end of the fibre.
46
Q

What produces Ultraviolet Radiation?

A

NAME?

47
Q

How do sun tanning lamps use UltraViolet Radiation?

A

NAME?

48
Q

How does security ink use Ultraviolet Radiation?

A

NAME?

49
Q

How do energy efficient lamps use Ultraviolet Radiation?

A

NAME?

50
Q

How does medical imaging use X-rays and Gamma rays?

A
  • x-ray photographs => x-rays pass through flesh but not denser materials like bone or metal, so the amount of radiation thats absorbed is what gives an x-ray imagine- x-ray images = negative images, as the densest parts which are exposed to fewest x-rays remain white, and the soft tissue parts where x-rays pass through without being absorbed turn black- gamma rays => medical tracer, as gamma-emitting isotopes can be traced as they pass through the body, because gamma rays can easily pass through the body to be detected
51
Q

How do medical treatments use x-rays and gamma rays?

A
  • radiographers use x-rays/gamma rays to treat cancer - radiotherapy- high doses of these rays kill living cells, so they’re directed towards cancer cells- however care has to be taken to avoid killing too many normal, healthy cells
52
Q

Damages of EM radiation

A
  • low frequency waves, like radio waves don’t transfer much energy and mostly pass through soft tissue without being absorbed- high frequency waves, like UV, x-rays, and gamma rays all transfer lots of radiation and can cause lots of damage
53
Q

UV radiation damage

A
  • damages surface cells like skin => sunburn + premature skin aging, also eye damage/possible blindness and increased risk of skin cancer
54
Q

x-rays and gamma rays damage

A

NAME?

55
Q

What does radiation dose take into account when measuring risk?

A

NAME?

56
Q

How are colours produced with visible light?

A

NAME?

57
Q

What are colour filters?

A

NAME?

58
Q

What does the temperature of an object depend on?

A

NAME?

59
Q

What does the temperature of the earth depend on?

A

NAME?

60
Q

What is a Leslie cube?

A
  • hollow water-tight cube made of a metal, e.g aluminium,- the 4 vertical faces have different surfaces; matt black, matt white, shiny metal, dull metal- used to investigate IR emission on by different surfaces
61
Q

Investigation IR emissions => required practical - method

A

NAME?

62
Q

Investigation IR emissions => required practical - results

A

NAME?

63
Q

Investigation IR absorptions => required practical - method

A
  • stick 2 ball bearings to 1 side of a metal plate with solid pieces of candle wax- other sides of the plate facing a flame/bunsen burner, these sides are then each painted matt black or silver
64
Q

Investigation IR absorptions => required practical - results

A

NAME?

65
Q

What is a perfect black body?

A

An object that absorbs all of the electromagnetic radiation that hits it. No radiation is reflected or transmitted by it. Best possible emitters of radiation too.

66
Q

What is intensity?

A

Power per unit area, i.e. how much energy is transferred to a given area in a certain amount of time.

67
Q

What happens as the temperature of an object increases? (2)

A

NAME?

68
Q

How many focal points does a converging/convex lens have?

A

2, either side of the lens

69
Q

What are the Refraction rules for a converging lens?

A
  1. Any incident ray travelling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens.2. A light ray that travels through the centre of the lens passes straight through.3. Any incident ray traveling through the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis.
70
Q

When the distance from the convex lens to the object is greater than 2F, what is;- the distance from image to object- type of image- size of image

A
  • between 2F and F- real, inverted- smaller than object
71
Q

When the distance from the convex lens to the object is equal to 2F, what is;- the distance from image to object- type of image - size of image

A
  • 2F- real, inverted- same as object
72
Q

When the distance from the convex lens to the object is between 2F and F, what is;- the distance from image to object- type of image- size of image

A
  • greater than 2F- real, inverted- larger than object
73
Q

When the distance from the convex lens to the object is equal to F, what is;- the distance from image to object- type of image- size of image

A

no image

74
Q

When the distance from the convex lens to the object is less than F, what is;- the distance from image to object- type of image- size of image

A

NAME?

75
Q

What kind of image does a concave lens produce?

A

NAME?

76
Q

Magnification Equation

A

magnification = image height/object height

77
Q

What are sound waves?

A

Longitudinal waves of vibrating particles that travel through mediums. As particles in mediums vibrate they hit the particles closest to them and so on, which causes the sound wave to move through the medium.Travels faster in solids than liquids, and liquids than gases as the particles are closer together.

78
Q

How does the speed of the sound wave affect frequency and wavelength?

A

NAME?

79
Q

What can sound waves sometime cause solid objects to do?

A

They can convert sound waves within a certain frequency range into vibrations.

80
Q

How do humans hear sound waves?

A

NAME?

81
Q

Between what frequencies of sound waves can humans hear?

A

20Hz - 20 000Hz (20KHz)

82
Q

What are ultrasound waves?

A

Sound waves with frequencies bigger than 20KHz, they therefore cannot be heard by people as they are outside of the necessary range for this.

83
Q

What is partial reflection?

A

When waves pass from one medium to another, some waves are reflected by the boundary between the two mediums, and some are transmitted/possibly refracted.

84
Q

What is the significance of partial reflection in ultrasound?

A
  • can point a pulse of ultrasound at an object, and whenever there is a boundary between 2 substances, some of the ultrasound is reflected back- the time it takes for reflections to reach the detector can be used to measure how far away boundaries are
85
Q

How is ultrasound used for medical imaging?

A

NAME?

86
Q

How is ultrasound used for industrial imaging?

A

NAME?

87
Q

How is ultrasound used for echo sounding?

A
  • type of sonar used by boats and submarines- ultrasound waves are used to find out depth of water they’re in, or to locate an object in deep water- the return time of reflection can be used to calculate the distance of the object etc, if you know the speed of sound in water
88
Q

What are seismic waves?

A

When there’s an earthquake, it produces seismic waves with travel through/across the earth.

89
Q

What are the 2 types of seismic waves?

A
  • P-waves => longitudinal, can travel through solids and liquids- S-waves => transverse, can’t pass through liquid materials
90
Q

What are seismometers?

A

Seismologists use detectors (seismometers) to detect seismic waves at different points on the surface of the planet.

91
Q

What happens when seismic waves reach a boundary between 2 materials?

A

NAME?

92
Q

What can seismologists do by measuring seismic waves?

A

NAME?