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PHYSICS GCSE EDEXCEL > TOPIC 4 - WAVES > Flashcards

TOPIC 4 - WAVES Flashcards

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1
Q

what are waves

A

Waves transfer energy and information without transferring matter

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2
Q

Transverse vs longitudinal waves

A
  • Longitudinal waves move parallel to direction of energy transfer
  • Transverse waves move perpendicular to direction of energy transfer
  • Longitudinal have compressions and rarefactions
  • Transverse have peaks and troughs
  • Longitudinal waves move in solids liquids gases
  • Transverse waves move in solids only
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3
Q

What is frequency

A

Number of wave cycles per second

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4
Q

What is wavelength

A

Distance peak to peak or compression to compression

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5
Q

What is period

A

Time taken to complete one wave cycle

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6
Q

Equation linking time and frequency

A

Time = 1/f

Frequency = 1/T

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7
Q

What is amplitude

A

Maximum displacement a point moves from rest position

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8
Q

Equation for wave speed

A

frequency x wavelength

or

distance/time

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9
Q

What can happen to waves when meeting a boundary?

A
  1. Reflected
  2. Refracted
  3. Transmitted
  4. Absorbed
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10
Q

What is reflection

A

When wave ‘bounces off’ boundary and stays in their original medium.

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11
Q

What is refraction

A

When wave changes speed and direction betweem 2 materials of different densities.

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12
Q

What happens to light ray if moving from a less dense to a more dense medium

A

It slows down and refracts towards normal.

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13
Q

What types are waves are sound waves

A

Longitudinal

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14
Q

What happens when sound waves are passed through liquids and gases?

A

particles vibrate back and forth as wave passes through.

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15
Q

What happens when sound waves are passed through solids?

A

Some energy is reflected, transmitted or absorbed. The sound wave causes changes in pressure on surface of the sold. It causes the particles in solid to vibrate (vibrations in solid can be longitudinal/transverse)

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16
Q

How does the human ear detect sound waves?

A
  1. sound waves enter ear canal
    2 sound waves make eardrum (thin membrane) vibrate
  2. Vibrations are passed onto ossicles (tiny bones) that amplify vibrations
  3. Vibrations are passed to liquid inside cochlea
  4. Tiny hairs inside cochlea detect vibrations and create impulses (electrical signals)
  5. Impulses travel along neurones in auditory nerve to reach the brain
17
Q

What is ultrasound

A

Frequency above 20 000Hz

18
Q

What is infrasound

A

Frequency below 20Hz

19
Q

What frequencies can humans detect

A

20-20 000Hz

20
Q

What are some uses of ultrasound

A
  1. Sonar
  2. Foetal scanning
21
Q

How does sonar work?

A

It uses ultrasound to detect objects underwater.
The pulse of ultrasound is sent underwater and is reflected off the ocean bottom.
The tiem it takes for the sound wave to return can be used to calculate depth.

22
Q

How does foetal scanning work?

A
  1. Gel is used on the stomach to stop ultrasound just reflecting off the skin.
  2. The transducer emits and recieves ultraosund waves.
  3. Some waves are reflected back to the transducer when reaching different mediums like fat or bone.
23
Q

Why is foetal scanning safe?

A

It is not ionising like X-rays.

24
Q

What type of waves do earthquakes produce?

A

P-waves and S-waves

25
Q

Compare P-waves and S-waves

A
  • Pwaves are longitudinal (can pass thru solids annd liquids)
  • Swaves are transverse (only thru solids)
  • S-waves can’t travel through (liquid) outer core
    -P waves can
  • P-waves are faster, S-waves are slower
26
Q

How are seimsic waves detected?

A

They are detected by seisometer all around Earth.

27
Q

What are the discoveries made by seismic waves?

A
  1. On the opposite side of the Earth to an earthquake, only P-waves are detected, not S-waves, suggesting mantle is solid as both waves pass through it, and suggesting outer core is liquid as no S-waves can penetrate it.
  2. Refractions between layers cause 2 shadow zones, where no P-waves are detected, suggesting inner core is solid as size and positions of these shadow zones indicate large refraction taking place.
28
Q

What happens when sound waves moves from less dense to more dense medium?

A

The wavelength decreases, frequency stays the same, speed decreases

PHYSICS GCSE EDEXCEL (12 decks)

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