P4 | waves Flashcards

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1
Q

what is sound with frequencies greater than 20,000Hz known as?

A

ultrasound

ultra = beyond

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2
Q

what is sound with frequencies less than 20Hz known as?

A

infrasound

infra = below

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3
Q

why does sound travel faster in liquids than in gases?

A

sound travels faster in liquids because the molecules are more tightly packed

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4
Q

wave speed formula

A

v = λ x f

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5
Q

what happens to frequency as sound waves travel from a less dense to more dense medium?

A

stays constant

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6
Q

what happens to wave speed as sound waves travel from a less dense to more dense medium?

A

increases

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7
Q

what happens to wavelength as sound waves travel from a less dense to more dense medium?

A

increases

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8
Q

why is it difficult to predict when an earthquake will happen?

A

movement of tectonic plates/release of energy in earth’s surface is sudden/random and it is difficult to measure when the release of energy will occur/plates will collide

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9
Q

order of earth’s structure (outer most to inner most)

A

crust (solid)
mantle (semi-solid)
outer core (liquid)
inner core (solid)

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10
Q

properties of p waves

A

primary waves (arrive first)

can travel through solids and liquids therefore they can pass through all of earth’s layers

longitudinal

shake the ground up and down

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11
Q

properties of s waves

A

secondary waves (arrive second)

can only travel through solids

transverse

shake the ground side to side

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12
Q

what should you always do to your answer for sonar pulse calculations?

A

divide by 2 at the end

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13
Q

how do scientists use seismic stations to locate where an earthquake happened?

A

work out the time between S and P waves to find out the time delay between them

d = s x t to calculate the distance the wave travelled

pick three stations and draw circles with the possible maximum distance

where they overlap is the epicentre (called triangulation)

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14
Q

what is S-P time

A

time difference between arrival of P waves and S waves

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15
Q

how is UV light used to check bank notes?

A

UV light absorbed by banknote which emits light into eye

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16
Q

uses of infrasound

A
  • investigating the internal structure of earth

- communication between elephants/dolphins

17
Q

uses of ultrasound

A
  • foetal scanning

- animal communication

18
Q

how does sound travel through air?

A

sound waves travel along vibrations of air particles parallel to the direction of energy transfer as longitudinal waves

19
Q

how are sound waves detected by an ear?

A
  • sound waves are collected by the outer ear (pinna)
  • the waves travel along the ear canal
  • the waves reach the eardrum and make it vibrate
  • small bones called ossicles amplify the vibrations
  • the cochlea turns these into electrical signals
  • the auditory nerve takes the signals to the brain
20
Q

how are ultrasounds used for foetal scanning?

A
  • ultrasound waves pass through the body
  • when they reach the boundary between fluid in the womb and the skin of the foetus, some of the wave is reflected back and detected
  • the exact timing and distribution of the waves are processed by a computer to produce a video image of the foetus