2.6 Waves Flashcards

1
Q

What is a wave?

A

A wave is a vibration or osciallation about an undisturbed position

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2
Q

What do waves transfer?

A

Waves transfer energy and information from one place to another

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3
Q

What do waves NOT transfer?

A

Matter

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4
Q

What are mechanical waves?

A

Mechanical waves are vibrations that need a medium to transfer energy.

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5
Q

What are electromagnetic waves?

A

Electromagnetic waves are oscillations that transfer energy through electrical and magnetic fields and doesn’t need a medium.

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6
Q

Give one example of a mechanical wave

A

Sound

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7
Q

Give one example of an electromagnetic wave

A

Light

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8
Q

What are transverse waves?

A

Transverse waves are waves where the vibrations are perpendicular to the direction of energy transfer

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9
Q

What are longtitudinal waves?

A

Longtitudinal waves are waves where the vibration is parallel to the direction of energy transfer

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10
Q

Give one example of where transverse waves are found

A

Ripples on a water surface

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11
Q

Give one example of where longtitudinal waves are found

A

Sound waves

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12
Q

What properties do longtitudinal waves have?

A

Longtitudinal waves have areas of compression and rarefaction

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13
Q

Students should be able to describe evidence that, for both ripples on a water surface and sound waves in air, it is the wave and not the water or air itself that travels.

A
  • A plastic duck on water will bob up and down, but will not travel with the wave as waves transfer energy, not matter or particles
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14
Q

Define the amplitude of a wave

A

The amplitude of a wave is from the undisturbed position to the peak.

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15
Q

Define the wavelength of a wave

A

The wavelength of a wave is the distance from one point of a wave to the equivalent point on the adjacent wave

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16
Q

Define the frequency of a wave?
What is it measured in?

A

The frequency of a wave is the number of waves passing a fixed point per second

Measured in Hz

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17
Q

Define the period of a wave

A

The period of a wave is the time taken for a wave to pass a fixed point

18
Q

Wave Period formula

A

Period = 1 / frequency
T = 1/f

Period (s), Frequency (Hz)

19
Q

Define wavespeed

A

A wavespeed is the speed at which energy is transferred through a medium

20
Q

Wavespeed formula

A

wavespeed = frequency × wavelength
v = f λ

Wavespeed (m/s), Frequency (Hz), Wavelength (m)

21
Q

Describe a method to measure the speed of sound waves in
air

A
  • 2 people must stand 500m away from each other
  • When one bangs 2 cymbals together, the other will see them crash together but will not hear it straight away
  • Use a stopwatch to time the interval between seeing the impact and hearing the sound
  • Repeat the experiment to get an average result
  • Use the formula Speed = Distance / Time to calculate the speed of sound in air
22
Q

Describe a method to measure the speed of ripples on a water
surface

A
23
Q

Where can waves be reflected, absorbed or transmitted?

A

Waves can be reflected, absorbed or transmitted at the boundary between two different materials such as air and water

24
Q

What happens to waves at the boundary between two materials?

A

Waves can be reflected, absorbed or transmitted at the boundary between two different materials such as air and water

25
Q

Describe the effects of the transmission of waves at material surfaces

A
  • Refraction can occur (possibility)
26
Q

What does the law of reflection state?

A

The angle of incidence = The angle of reflection

27
Q

What is the normal?

A

The normal is a line at 90° to the surface of a material

28
Q

How are the angle of incidence and angle of reflection measured?

A

The angles of incidence and reflection are measured between the ray and the normal

29
Q

What are the most reflective surfaces?

A

Flat and smoother surfaces are the most reflective

30
Q

What is specular reflection?

A

Specular reflection is when light travelling towards a surface is all reflected in a single direction

31
Q

What is diffuse reflection?

A

Diffuse reflection is when light is reflected off a rough surface and is scattered in different directions

32
Q

Why are rough surfaces the least reflective?

A

Because the light scatters in all directions

33
Q

What happens when a wave is absorbed?

A

When a wave is absorbed, the energy of the wave is transferred to the particles of the material

34
Q

What is transmission?

A

Transmission is when a wave passes through a substance

35
Q

Why may a transmitted wave have a lower amplitude?

A

Because of partial absorption

36
Q

What are sound waves?

A

Sound waves are vibrations of air molecules

37
Q

Why are sound waves longtitudinal?

A

Sound waves are longitudinal because they transfer energy in the same direction that the air particles vibrate along

38
Q

How can sound waves travel through solids?

A

They cause vibrations of particles in the solid

39
Q

Why do sound waves travel faster in a solid that in a gas?

A

Because the particles are much closer together so they can pass on the vibrations more easily

40
Q

Explain how are sound waves detected within the ear?

A
  • Sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound
  • The sound waves are converted into vibrations and travel through as vibrations
  • The conversion of sound waves to vibrations of solids works over a limited frequency
    range, which restricts the limits of human hearing
41
Q

Why can’t sound waves travel through a vacuum?

A

Sound waves need a medium in order to travel

42
Q

What is the range of normal human hearing?

A

20 Hz to 20 kHz