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Physics > Sound And Seismic Waves > Flashcards

Sound And Seismic Waves Flashcards

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1
Q

What are transverse waves

A

The movement of a transverse wave is at a right angle to the direction in which the energy is travelling

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2
Q

What are longitudinal waves

A

The movement of a longitudinal wave is in the same direction as which the energy is travelling in

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3
Q

What is frequency

A

The number of waves per second

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4
Q

What is the wave equation

A

Wave speed = frequency X wavelength

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5
Q

What is amplitude

A

Maximum displacement of the wave from the point of equilibrium

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6
Q

What is the wavelength

A

The distance from trough to trough

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7
Q

The frequency of a sound produced by a guitar string is 440Hz. What does this mean

A

440 vibrations per second

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8
Q

What does ultrasound mean

A

Any frequency over 20,000Hz

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9
Q

What is infrasound

A

Any frequency under 20Hz

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10
Q

What happens to the particles in sound

A

The particles vibrate back and fort and collide with eachother, passing the energy on. The particles vibrate in the same direction as the energy travels.

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11
Q

Uses of ultrasound

A
  • frequency above 20,000Hz
  • commonly used to create images medically
  • is based on the reflection and transmission of a wave at a boundary
  • higher frequencies provide better quality, but are more readily absorbed by the skin
  • transmitted from the probe through the gel into the body
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12
Q

Used of infrasound

A
  • frequency below 20Hz
  • is detected using a microphone
  • scientists can use infrasound to track the passage of meteors through the atmosphere
  • infrasonic sound can be the result of a volcanic eruption
  • elephants and giraffes use infrasound to communicate between herds over long distances
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13
Q

Echolocation

A
  • animals such as bats and Dolphins
  • use high frequency sounds to create a mental image of their location
  • emit calls to the environment and listen to the echoes of those calls that return from various objects near them
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14
Q

How is infrasound used for tracking animals

A

The frequency can be detected using machines and vibrations caused by their movement to locate animals

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15
Q

What is sonar

A

It is a technique that uses sound propagation

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16
Q

What is sonar used for

A

For navigating, communicating or detecting objects on or under the surface of the water

17
Q

How does crack detection work

A

A wave is reflected from the bottom of the sample and is then reflected from the flaw to the transmitter/receiver

18
Q

What is crack detection

A

Sonar is used with time taken to receive an echo being measured. It is used to detect cracks and defects which weakens metal, bars and pipes

19
Q

What are primary waves

A

Longitudinal waves

20
Q

What are secondary waves

A

Transverse waves

21
Q

What do primary waves travel through

A

Solids and liquids

22
Q

What do secondary waves go through

A

Solids only

23
Q

What is the crust

A

Relatively think and rocky

24
Q

What is the inner core like

A

Made from solid nickel and iron

25
Q

What is the outer core like

A

Made from liquid nickel and iron

26
Q

What is the mantle like

A

Has properties of a solid, but can flow very slowly

27
Q

Explain why we think Earth had a liquid core which contains a solid inner core?

A
  • Earth gives out both P and S waves
  • S waves cannot travel through a liquid
  • No S waves pass through the middle of the Earth
  • P waves can travel through the liquid core and are detected
  • however, their direction is refracted, meaning there is a different material in the centre of the core, such a solid
28
Q

What are the two main types of wave

A

Transverse

Longitudinal

29
Q

A scientist can work out the location of an earthquake by:

A
  • using a seismometer to pick up vibrations
  • calculating the time difference between the arrival of the s and p waves received to find how far the source is away
  • comparing the data from atleast 3 different seismometers to find the epicentre
30
Q

Why is it hard to predict when and where an earthquake will occur

A

They tend to occur along fault lines, but it is hard to predict where along it the pressure will build up. There are no known precursors for earthquakes

31
Q

Where is the epicentre

A

The place of origin of the earthquake

32
Q

Where is the focus

A

Directly above the origin of the earthquake

33
Q

How is ultrasound used to create medical images

A
  • a pulse is sent of ultrasound from the probe
  • the gel between the probe and skin allows the ultrasound to travel through the body
  • then some of the ultrasound waves reflect from the boundary, which in this case is the baby’s head
  • the time between sending the pulse and detecting reflecting waves is used to calculate the depth / distance to the baby

Physics (6 decks)

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