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Physics Paper 2 > Waves > Flashcards

Waves Flashcards

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1
Q

Describe transverse waves.

A
  • the oscillations are perpendicular to the direction of the energy transfer (at right angles)
  • the oscillations go up and down
  • but direction of energy transfer is sideways
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2
Q

Longitudinal waves

A

Oscillations are parallel to the direction of energy transfer.
Require a medium to travel in.

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3
Q

Define frequency?

A

Number of waves that pass a certain point per second.

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4
Q

Describe how sound waves work in a microphone.

A
  • when sound waves hit the paper cone, this causes it to vibrate
  • microphone converts this into electrical signals.
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5
Q

Describe how sound waves work in the ear.

A
  • sound waves in the air are funneled into the ear where they hit the eardrum
  • ear drum is a thin membrane
  • sound waves cause the eardrum and other parts of the inner ear to vibrate
  • causes the sensation of sound.
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6
Q

State the normal human frequency range of hearing.

A

20-20000Hz

-frequencies outside this range may not be able to make the ear drum vibrate

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7
Q

Why do sound waves travel so much faster in solids?

A
  • the particles are much closer together

- the vibrations can pass more easily between them

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8
Q

Why does frequency not change when a wave changes medium?

A
  • this is because the waves would have to be destroyed or created at the boundary
  • which isn’t possible
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9
Q

What is the problem with cathode ray oscilloscopes?

A
  • represent sound waves as if they were transverse waves

- but sound waves are longitudinal

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10
Q

What is a reflected sound wave?

A

An echo.

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11
Q

Why can sound waves only travel through mediums?

A
  • sound waves only move by particles vibrating

- sound waves cannot pass through a vacuum as there are no particles

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12
Q

What is ultrasound?

A

Sound waves with a frequency higher than the upper limit of human hearing, so it is at least 20,000Hz

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13
Q

Does ultrasound scanning work for any organ surrouned by bone?

A

No

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14
Q

What is the speed of ultrasound in water?

A

1600m/s

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15
Q

When can refraction happen?

A

When any wave changes speed as it passes from one medium to another.

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16
Q

Rays of light entering a glass block.

A
  • when light passes from the air into the glass, the velocity of light decreases
  • this causes the direction of the waves to change
  • when waves slow down, they bend towards the normal
  • light waves now pass through the glass block
  • when waves pass from the glass into the air, their velocity increases
  • when waves speed up, they bend away from the normal
  • causes the image of the object to appear to have shifted position
17
Q

When do waves NOT change direction when entering/leaving a medium?

A

If the waves enter or leave the medium at right angles to the surface (along the normal).

18
Q

Describe ultrasound pulses reflecting off of a kidney

A
  • if we know the time it takes for the ultrasound pulse to leave the probe and bounce off the kidney, and then be collected by the probe
  • we can calculate the distance between the porbe and the kidney
19
Q

Why is ultrasound safer than x-rays?

A

-doesn’t cause any mutations or increase the risk of cancer

20
Q

Why are wavefronts used?

A

Make it easier to visualise lots of waves moving together

21
Q

Why do earthquakes happen?

A
  • due to a sudden movement between the tectonic plates in the earth’s crust
  • these cause seismic waves which carry energy away from the earthquake
22
Q

Describe p-waves

A
  • longitudinal
  • can pass through both solids and liquids
  • travel faster than s-waves
23
Q

Describe s-waves

A
  • transverse waves

- s-waves can only travel through solids

24
Q

Why do seismic waves travel in curved paths?

A

-due to density changes in the earth

25
Q

How do scientists know about the liquid outer core?

A
  • s waves cannot pass through a liquid
26
Q

Why are there p-wave shadow zones?

A
  • p waves travel faster in solids than in liquids
  • they slow down as they enter the liquid outer core
  • which causes them to refract as they leave or enter
27
Q

How did scientists know about the solid inner core?

A

-faint p-waves can be detected on the p-wave shadow zone.

Physics Paper 2 (5 decks)

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