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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

Define transverse wave

A

A wave which travels at 90 degrees to direction of energy transfer

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2
Q

Define longitudinal wave

A

A wave which travels parallel to direction of energy transfer

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3
Q

Examples of transverse waves

A

Light waves, Surface water waves

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4
Q

Examples of longitudinal waves

A

Sound waves, pressure waves

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5
Q

What do waves transfer?

A

Waves transfer energy but NOT matter

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6
Q

Amplitude

A

The point of max. displacement from equilibrium position

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7
Q

Frequency

A

Number of waves produced/passing a particular point per second

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8
Q

Time period

A

The time taken for a wave to complete 1 cycle

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9
Q

Wavelength

A

The distance between a point on one wave to the same point on the next wave, eg peak to peak

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10
Q

What formula links time period and frequency?

A

T = 1/f OR F = 1/T

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11
Q

What formula links wavespeed, wavelength and frequency?

A

Wavespeed = frequency x wavelength

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12
Q

What is the unit of wavelength?

A

meters, m

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13
Q

What is the unit of time period?

A

Seconds, s

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14
Q

What is the unit of speed?

A

meters per second, m/s

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15
Q

What is the unit of frequency?

A

Hertz, Hz

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16
Q

What determines the pitch of a sound?

A

The frequency

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17
Q

What determines the loudness of a wave?

A

The amplitude

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18
Q

If a wave has a low frequency and a low amplitude, what is the pitch and loudness like?

A

Low pitch, low volume

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19
Q

If a wave has high frequency and high amplitude , then what’s the wave like?

A

High pitch, high volume

20
Q

If a wave has low frequency and high amplitude, what’s the wave like?

A

Low pitch, high volume

21
Q

If a wave has a high frequency and a low amplitude, what’s the wave like?

A

High pitch, low volume

22
Q

Speed of sound in air

A

330m/s

23
Q

Speed of sound in water

A

1500m/s

24
Q

Speed of sound in steel

A

5000m/s

25
Q

How does medium affect the speed of sound?

A
  • As density of medium increases, so does speed of sound.
  • Sound travels fastest in a solid where the particles are close together (as solids are the most dense) and they can transfer vibrations faster between particles
  • in gas + liquids, particles are further away (less dense) so vibrations take longer to pass between particles
26
Q

What is the range of human hearing?

A

20-20,000Hz

27
Q

What are the uses of ultrasound?

A
  • prenatal ultrasound scans
  • crack detection in machinery
  • breaking kidney stones
28
Q

How is ultrasound used in prenatal scans?

A
  • probe emits + receives the waves
  • ultrasound transmits through the tissue
  • the waves are reflected whenever there is a change in density to create an image on the screen
  • the time taken to recieve echo x speed of sound = depth of fetus
    Which is done multiple times to form image
29
Q

How is ultrasound used in crack detection in machinery?

A
  • the transceiver transmits ultrasound through the metal
  • waves are reflected back to transceiver when the crack is detected to see how deep in the crack is
  • time taken and speed through medium is multiplied to find how deep the crack is
30
Q

Order of waves in EM spectrum

A

Radiowaves, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma rays

31
Q

Common properties of all EM waves

A
  • all are transverse
  • all travel at 3 x 10^8m/s in a vacuum
  • all can be reflected, refracted and diffracted
32
Q

Uses of Radiowaves

A
  • radio + TV signals
  • long wave radio signals are broadcasted by transceivers and and are reflected by the atmosphere around the world to other transceivers
33
Q

Uses of microwaves

A
  • cooking wood w large water content + mobile & satellite comms
  • water molecules in food absorb large amts of microwaves so food gets hot and cooks
  • are able to transmit though atmosphere to satellites
34
Q

Uses of infrared

A
  • cooking food on grills + short range data comms (TV remotes)
  • thermal energy emits from grill into air and absorbed by food
  • waves transmit through air from remote, and energy absorbed quickly so are used for short distances
35
Q

Uses of visible light

A
  • traffic systems + glasses/ contacts
  • coloured light transmits through the air and is absorbed by eyes
  • refraction of light through curved glass is absorbed by eyes to correct vision
36
Q

Uses of ultraviolet

A
  • security tagging banknotes, sterilising, tanning
  • fluorescent ink absorbs UV and reflects white light into eyes
  • bacteria absorbs UV and is killed
  • suncream absorbs and/or reflects UV instead of it being absorbed by skin
37
Q

Uses of X-rays

A
  • airport security scanners, scanning of skeleton
  • waves are transmitted through bags and picked up by a receiver to form an image
  • transmitted through body tissue but reflected by bones so the film has a shadow of the bones to identify cracks
38
Q

Uses of gamma rays

A
  • radiotherapy cancer treatment, medical tracer
  • high energy waves are directed to the cancer which absorbs them and the cells die
  • patient is injected w radioactive tracer which absorbs gamma so blockages can be seen during a scan
39
Q

What 3 parts of the EM spectrum are ionising?

A

UV, X-rays and gamma rays

40
Q

Why are UV, X-rays and gamma rays ionising?

A

have the highest frequency = highest energy which means that they’re more dangerous

41
Q

Why is ionising radiation dangerous?

A
  • overexposure of ionising radiation causes atoms in cells to lose electrons, ionising them
  • this can mutate cells and lead to cancer
42
Q

Why is overexposure to visible light dangerous?

A

harms the eyes by damaging the retinas

43
Q

Why is overexposure to infrared dangerous?

A

Burns the skin and tissue

44
Q

What is the Doppler effect?

A

The apparent shift in wavelength when a source moves relative to an observer. As wavelength decreases, frequency increases. The faster the sourceis moving relative to the observer, the more pronounced the difference in pitch and volume.

45
Q

How does the Doppler effect work?

A
  • as the source gets closer to the observer, there is an apparent increase in frequency which results in a higher volume and pitch, called blue shift
  • as the source moves away from the observer, there is an apparent decrease in frequency which results in a lower volume and pitch, called red shift

Physics (10 decks)

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