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Physics > topic 6 - Waves > Flashcards

topic 6 - Waves Flashcards

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1
Q

what are the two types of waves?

A
  • longitudinal waves
  • transverse waves
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2
Q

what is a transverse wave?

A

a wave for which the oscillations are perpendicular to the direction of energy transfer

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3
Q

what is a longitudinal wave?

A

a wave for which the oscillations are parallel to the direction of energy transfer

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4
Q

what are two examples of transverse waves?

A
  • electromagnetic waves
  • seismic s-waves
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5
Q

what are two examples of longitudinal waves?

A
  • sound waves
  • seismic p-waves
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6
Q

what are the two parts of a longitudinal wave called?

A

compressions and rarefactions

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7
Q

what is the frequency of a wave?

A

the number of waves that pass a given point each second

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8
Q

what is the unit used for frequency?

A

Hertz, Hz

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9
Q

what does a wave transfer?

A

energy

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10
Q

what word is used to describe when a wave bounces off a surface?

A

reflection

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11
Q

when does reflection occur?

A

when a wave hits a boundary between two media and does not pass through, but instead stays in the original medium

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12
Q

what is the law of reflection?

A

the angle of incidence = the angle of reflection

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13
Q

what are echoes an example of?

A

sound waves being reflected off a surface

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14
Q

what surfaces are the most reflective?

A

the smoother the surface, the stronger the reflected wave

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15
Q

what surfaces are the least reflective?

A
  • rough surfaces are the least reflective
  • this is because the light scatters in all directions
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16
Q

what do opaque surfaces reflect?

A
  • opaque surfaces will reflect what is not absorbed by the material
  • the electrons will absorb the light energy and then reemit it as a reflected wave
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17
Q

when does transmission occur?

A

when a wave passes through a substance

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18
Q

how does the transparency of a material affect light waves?

A

the more transparent the material, the more light will pass through

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19
Q

what must be occur for transmission to happen?

A

for the process to count as transmission, the wave must pass through the material and emerge from the other side

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20
Q

when does absorption occur?

A

when energy is transferred from the wave into the particles of substance

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21
Q

How is light absorbed?

A
  • light will be absorbed if the frequency of light matches the energy levels of the electrons
  • the light will be absorbed, and then reemitted over time as heat
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22
Q

what does it mean when an object appears red?

A
  • only red light has been reflected
  • all the other frequencies of visible light have been absorbed
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23
Q

what are sound waves?

A
  • vibrations of air molecules
  • can travel through solids causing vibrations in the solid
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24
Q

what happens when a sound wave hits a solid?

A
  • the variations in pressure cause the surface of the solid to vibrate in sync with the sound wave
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25
Q

What do sound waves consist of?

A
  • compressions - regions of higher density
  • rarefactions - regions of lower density
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26
Q

what happens when sound moves from a denser medium to a less dense medium?

A
  • the wavelength of the sound waves increases
  • the frequency of the sound wave stays the same
  • the velocity of the sound wave increases
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27
Q

what happens when sound moves from a less dense medium to a denser medium?

A
  • the wavelength of the sound wave decreases
  • the frequency of the sound wave stays the same
  • the velocity of the sound wave decreases
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28
Q

what is an angle of incidence?

A

the angle between the incident ray and the normal

29
Q

what is the relationship between the angle of incidence and the angle of reflection?

A

they are equal

30
Q

what is the frequency range of human hearing?

A

20Hz - 20KHZ

31
Q

what are ultrasound waves?

A

sound that vibrates at frequencies above 20,000Hz

32
Q

what are some uses for ultrasound waves?

A
  • prenatal scanning
  • industrial imaging
  • sonar
33
Q

describe how sound waves travel through the human ear

A
  • the sound wave travels down the auditory canal towards the eardrum
  • the pressure variations created by the sound wave exert a varying force on the eardrum causing it to vibrate
  • the vibration pattern of the sound waves creates the same pattern of vibration in the eardrum
  • the eardrum vibration is transferred to the three small bones (hammer, anvil, stirrup)
  • the vibrations are transferred to the inner ear where nerve cells detect the sound and send a message to the brain giving the sensation of sound
34
Q

what are the uses of sound waves?

A

echo sounding - used by shipping to detect the ocean floor
ultrasound - used to look inside the human body
ultrasound crack detection- to find cracks in rail tracks
reflection seismology - to detect oil and gas underground
seismic activity - can be used to investigate the structure of the earth

35
Q

describe the prenatal scanning method

A
  • ultrasound waves are produced in the transducer
  • some of the ultrasound waves are reflected each time it meets a different material such as bone, muscle or fluid
  • the reflected wave is detected by the transducer each time taken is measured
  • using the time taken, the distance to different parts of the fetus is calculated and image is built up
36
Q

describe the prenatal scanning method.

A
  • ultrasound waves are produced in the transducer
  • some of the ultrasound waves are reflected each time it meets a different material such as bone, muscle or fluid
  • the reflected wave is detected by the transducer each time taken is measured
  • using the time taken, the distance to different parts of the fetus is calculated and image is built up
37
Q

what are the advantages of ultrasound waves?

A
  • the ultrasound reflects all types of tissue so can be used to scan many organs or tissues
  • x-rays used for bones are ionising. Ultrasound is non-ionising
38
Q

how is ultrasound used by ships to determine the distance to shoals of fish?

A
  • ultrasound signal is produced by the ship
  • ultrasound signal reflected by the fish
  • reflected signal detected by the ship
  • time taken between emission and detection measured
  • then use distance = velocity x time
39
Q

what natural event causes seismic waves to be produced?

A
  • earthquakes
40
Q

what types of waves do seismic waves produce?

A

P- waves
S-waves

41
Q

what is the difference between the mediums that P-waves and S-waves can travel through?

A
  • P-waves travel through both solids and liquids
  • S-waves are transverse, seismic waves, they only travel through solids
42
Q

what is the nearest point on the Earth’s surface called?

A

epicentre

43
Q

what are shadow zones?

A

areas that are unable to detect seismic waves

44
Q

What happens to P and S waves as they travel through the mantle?

A
  • P and S waves bend as they travel through the mantle as their speed changes with depth
45
Q

what does the discovery of shadow zones suggest about the outer core?

A

the outer core is liquid, as S-waves are transverse waves so they cannot pass through

46
Q

why do both waves change direction as they go deeper into the earth?

A

due to the change in medium, they change speed and refract

47
Q

what is used by lenses to form an image?

A

refraction

47
Q

what wave is used by lenses to form an image?

A

refraction

48
Q

how does a convex lens form an image?

A

parallel rays of light are refracted and brought together at a point known as the principal focus

49
Q

what is meant by the focal length of a lens?

A

the distance from the lens to the principal focus

50
Q

what is the difference between the image produced by a convex and a concave lens?

A
  • convex lenses can produce real or virtual images
  • concave lenses can only produce virtual images
51
Q

why does magnification not have a unit?

A
  • it is the ratio between image height and object height
  • ratios do not require units
52
Q

what determines the colour of visible light waves?

A

the wavelength and frequency of the light waves

53
Q

what colour of visible light has the highest frequency?

A

blue

54
Q

what colour of visible light has the largest wavelength?

A

red

55
Q

what is meant by the term “specular reflection”?

A

reflection from a smooth surface in a single direction

56
Q

what happens to the wavelengths of light that arent reflected by an opaque object?

A

any wavelengths that aren’t reflected are absorbed by the object

57
Q

what colour does an object appear if all wavelengths are reflected in equal amounts?

A

white

58
Q

what colour does an object appear if all wavelengths are absorbed?

A

black

59
Q

what do all objects emit and absorb?

A

infrared radiation

60
Q

what happens to the infrared radiation emitted by an object as temperature increases?

A
  • the hotter the object, the more infrared radiation it will emit
61
Q

what is a perfect black body?

A
  • an object that absorbs all of the radiation incidents on it
  • a black body does not reflect or transmit any radiation
  • since a good absorber is also a good emitter, a perfect black body would be the best possible emitter
62
Q

what is a perfect black body?

A
  • an object that absorbs all of the radiation incidents on it
  • a black body does not reflect or transmit any radiation
  • since a good absorber is also a good emitter, a perfect black body would be the best possible emitter
63
Q

what does the temperature of the Earth depend on?

A
  • the rates of absorption - emission of radiation
  • reflection of radiation into space
64
Q

how much radiation does a perfect black body reflect or transmit?

A

none

65
Q

what can be said about the rates of emission and absorption for a body at constant temperature?

A
  • the body is absorbing and emitting radiation at the same rate
66
Q

how do emergency blankets keep a trauma victim warm?

A
  • rescue teams use light-coloured, shiny emergency blankets to keep accident survivors warm
  • a light, shiny outer surface emits a lot less radiation than a dark, matt surface
  • this keeps the patient warm, as less infrared radiation is emitted than if an ordinary blanket had been used
67
Q

what is the amplitude of a wave?

A
  • the maximum displacement of a point on a wave away from its undisturbed position

Physics (8 decks)

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