Waves Flashcards

1
Q

What are transverse waves?

A

When the medium of a wave vibrates at right angles

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2
Q

What type of waves are sound waves?

A

Longitudinal waves

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3
Q

What are electromagnetic waves?

A

Transverse waves that do not need a medium (material) through which to travel

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4
Q

What is frequency?

A

The number of waves passing a point each second; measured in hertz (Hz)

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5
Q

What is period?

A

The length of time it takes one wave to pass a given point

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6
Q

What is wavelength?

A

The distance from a point on one wave to a point in the same position on the next wave (m) - peak to peak or trough to trough

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7
Q

What is amplitude?

A

The maximum distance of a point on the wave away from its rest position (m)

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8
Q

What is velocity of a wave?

A

The speed of the wave in the direction it is travelling (m/s)

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9
Q

How do you calculate wave speed (m/s)?

A

WAVE SPEED (M/S) = FREQUENCY (HZ) X WAVELENGTH (M)

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10
Q

What does the speed of a wave depend on?

A

The medium through which it is travelling

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11
Q

How can you find the speed of sound?

A

By measuring the time it takes for a sound to travel a certain distance:

  • Measure time it takes for a wave to travel between 2 fixed points such as buoys
  • Calculate speed from the time and distance between the 2 points
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12
Q

What is refraction?

A

The change in direction when light moves into a different medium

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13
Q

Where does refraction happen?

A

At the interface (boundary) between the 2 media

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14
Q

What is the normal line?

A

the line at right angles to the interface

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15
Q

Why does refraction happen?

A

Light travels at different speeds in different media, and so as light passes the interface between one medium and another it changes speed; this change in speed causes the direction of the light to change

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16
Q

What does the bend of light depend on in refraction?

A

How fast the light travels in the 2 media and the angle of the light hitting the interface

17
Q

What is transmission?

A

When the wave passes through the material and is not absorbed/refelcted

18
Q

What is absorption?

A

When the wave disappears as the energy it is carrying is transferred to the material

19
Q

What is light from light bulbs/the Sun called?

A

White light, and is made up of a mixture of different frequencies of light; we see these different frequencies as different colours

20
Q

What does a sound wave cause?

A

Changes in pressure on the surface of a solid, which causes particles in the solid to vibrate and so the disturbance is passed from the air to the solid

21
Q

How do we hear things?

A
  1. Sound waves enter the ear canal
  2. Eardrum is a thin membrane and sound waves make it vibrate
  3. Vibrations passed on to tiny bones (ossicles) which amplify the vibrations (make them bigger)
  4. Passed on to the liquid inside the cochlea
  5. Tiny hairs inside the cochlea detect these vibrations and create impulses which are electrical signals
  6. Impulses travel along neurones in the auditory nerve and reach the brain
22
Q

What is the cochlea?

A

A coiled tube containing a liquid

23
Q

What does the cochlea to detect different sounds best?

A

Different thickness of the membrane at different parts of the cochlea, as different sound waves are detected best at different frequencies

24
Q

What is ultrasound?

A

Sounds made by waves with higher frequencies above 20,000 Hz (20 kHz)

25
Q

What do sonar equipment do?

A

They are carried on ships or submarines that find the depth of the sea or detect fish using a loudspeaker that emits a pulse of ultrasound which spreads out through the water and some of it is reflected by the sea bed. A special mic detects the echo and the equipment measures the time between the sound being sent out and the echo returning. The distance is then calculated by speed X time

26
Q

What is the gel in ultrasound scans for babies used for?

A

To stop the ultrasound just reflecting from the skin of the mother

27
Q

What is infrasound?

A

Sounds with a frequency less than 20 Hz

28
Q

What are the vibrations caused by earthquakes called?

A

Seismic waves

29
Q

How can seismic waves be detected?

A

By longitudinal P waves and transverse S waves using a seisometer

30
Q

What can P waves travel through?

A

Liquids and gases

31
Q

What can S waves travel through?

A

Solids

32
Q

What is the S wave shadow zone?

A

A large area of Earth on the opposite side to the earthquake where no S waves are detected

33
Q

Why does the shadow zone of S waves occur?

A

Because part of the interior of the Earth is liquid, which S waves cannot travel through