Waves 2 Flashcards

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1
Q

What is a transverse wave?

A

A wave where vibrations occur perpendicular to the direction the wave is travelling

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2
Q

What is a longitudinal wave?

A

A wave where vibrations occur parallel to the direction the wave is travelling

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3
Q

Define amplitude

A

The maximum distance between the peak or trough of a wave and its equilibrium point

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4
Q

Define wavefront

A

A horizontal line drawn linking all the peaks in a set of waves

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5
Q

Define wavelength

A

The distance from point on a wave to the same point on the next wave

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6
Q

Define frequency

A

Number of waves per second

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7
Q

Define the period of a wave

A

Time taken to complete one wave cycle

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8
Q

Equation for wave speed

A

Wave speed = frequency x wavelength

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9
Q

Equation for wave frequency

A

Frequency = 1 / time period

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10
Q

What property do all waves have in common?

A

They can be reflected and refracted

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11
Q

What is the Doppler effect?

A

The change in frequency and wavelength caused by relative movement of the source of wave or observer

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12
Q

Give an example of the Doppler effect in sound waves

A
  • When an ambulance goes past you the siren decreases in pitch
  • This is because the wavelength of the sound waves increases
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13
Q

Give an example of the Doppler effect in light waves

A
  • Light from distant planets looks red (it’s red-shifted)
  • Because planets are moving away from us so wavelength becomes longer and therefore moves to the red spectrum
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14
Q

Which EM waves can be used in cooking?

A

Microwaves and infrared radiation

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15
Q

Which EM wave causes burns?

A
  • Infra-red radiation
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16
Q

Which EM wave causes skin cancer

A

UV

17
Q

What are the dangers of X-rays and gamma rays?

A
  • Ionising radiation
  • Mutation
  • Cancer
18
Q

What do all EM waves have in common?

A
  • All transfer energy
  • All travel at the same speed in a vacuum
  • Can be reflected, refracted and diffracted
  • All transverse waves
19
Q

What are the advantages of optic fibres?

A
  • Carry more information per second
  • More secure
20
Q

How are x-rays and gamma rays similar?

A
  • Both short wavelength EM waves
  • Carry lots of energy per second
21
Q

How do x-rays and gamma rays differ?

A
  • X-rays are made when electrons moving at high speeds are stopped
  • Gamma rays are released from unstable nuclei
  • Gamma is more penetrative
  • Gamma has shorter wave length
22
Q

Describe the properties of light waves

A
  • Transverse wave
  • Transfer energy
  • Can be reflected, refracted, diffracted
  • A wave where vibrations occur perpendicular to the direction the wave is travelling
23
Q

What is a normal line?

A

A line drawn perpendicular to the mirror

24
Q

What is the law of reflection?

A
  • Angle of incidence = angle of reflection
25
Q

What is refraction?

A

A change in direction of waves when they travel across a boundary from one medium to another

26
Q

Describe how a light ray changes direction when it enters and leaves a glass block

A
  • Bends towards the normal as it enters the block
  • Bends away from the normal as it leaves the block
27
Q

Snell’s law (refractive index)

A

n = sin i / sin r

28
Q

Define critical angle

A

Angle of incidence beyond which rays of light are totally internally reflected

29
Q

Define total internal reflection

A
  • When the angle of incidence is greater than the critical angle
  • All light is reflected, none is refracted
30
Q

How do optical fibres work?

A
  • Total internal reflection
  • Core of fibre made out of glass with high refractive index
  • Cladding is made out of glass with lower refractive index
  • Light entering core is at an angle greater than the critical angle so light is TIR
31
Q

Give examples of the use of optical fibres

A
  • Endoscope - used in keyhole surgery
  • Communication as less energy is lost when compared to using copper wiring
32
Q

Critical angle

A

sin c = 1 / refractive index (n)

33
Q

Describe the properties of sound waves

A
  • Longitudinal waves
  • Transfer energy
  • Can be reflected, refracted and diffracted