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Physics by Thaidz > Waves > Flashcards

Waves Flashcards

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1
Q

what is wavelength? (λ)

A

distance from one peak to the next

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2
Q

what is frequency? (f)

A

how many complete waves pass per second

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3
Q

what is the measurement for frequency ?

A

hertz (Hz) 1 Hz = 1 wave per second

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4
Q

What is amplitude ?

A

height of the wave (rest to crest) / (trough to rest)

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5
Q

what is a period ? (T)

A

time (s) it takes for one complete wave

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6
Q

Frequency =

A

1 / period ( time (T) )

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7
Q

wave speed =

A

frequency x wavelength (v = f x λ)

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8
Q

1 MHz = how many Hz?

A

1 000 000 Hz

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9
Q

1 kHz = how many Hz?

A

1 000 Hz

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10
Q

Most waves are …?

A

Transverse

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11
Q

Give some examples of transverse waves

A

light and all other EM waves
slinky wiggled up and down
ripples on water

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12
Q

Give some examples of longitudinal waves

A

sound and ultrasound
shock waves ( like seismic waves )
slinky pushed inwards

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13
Q

Describe the vibrations in transverse waves

A

vibrations are at 90° to the direction energy is transferred by the wave

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14
Q

Describe the vibrations in longitudinal waves

A

vibrations are along the same direction the wave transfers energy

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15
Q

What is diffraction ?

A

waves bend around edges and through gaps
waves spread out
longer wavelength / narrow gap = more diffraction

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16
Q

Visible light colours order

How do they link to wave length?

A 
Red - longest wavelength
Orange 
Yellow
Green
Blue
Indigo
Violet - shortest wavelength
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17
Q

Give the order of EM waves (including wavelength and frequency)

A

Radio waves (longest wavelength/lowest frequency) - microwaves - infra red - visible light - ultra violet - x rays - gamma rays (shortest wavelength/highest frequency)

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18
Q

what speed do EM waves travel at ?

A

all travel same speed through free (vacuum)

they are also all transverse

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19
Q

Describe radio waves

Uses ?

A

used for communications/TV/FM radio
long radio waves can travel around the world as they diffract around earths curve
short radio waves can also travel great distances as they reflect from the ionosphere

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20
Q

what is the ionosphere ?

A

an electrically charged layer in Earth’s upper atmosphere

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21
Q

Describe how microwave satellites work

A

used for satellite communication (like satellite TV)
signal transmitted to a transmitter in space
transmitter transmits signal to satellite dish on ground

22
Q

Describe how microwave ovens work

A

used for cooking, have different wave length to microwave communications
these are absorbed by water molecules in food and the energy is conducted or convected

23
Q

What are the uses for infrared radiation ?

A

used for heating and monitor temp
used in grills / toasters to cook food
used in radiators to radiate heat
used in night vision, turns infrared into electrical sign displayed on screen

24
Q

Describe how visible light signals work (optical fibres)

Uses ?

A

used for communication with light signals which carry data as pulses of light
they work by bouncing waves of light off sides of a narrow core
light enters at certain angle and is reflected repeatedly until comes out
used in telephone / internet cables and medical purposes (see inside body)

25
Q

Describe how visible light photography works

A

camera uses lens to focus light onto electronic sensor
lens aperture controls how much light enters camera
shutter speed determines how long sensor exposed to light

26
Q

What are the uses for ultraviolet ?
How are they made safe ?
Advantages ?

A

used in florescent lamps
they use UV radiation to emit visible light
safe to use as UV is absorbed by phosphor coating
more energy-efficient than filament light bulbs

27
Q

What are the uses for X-Rays ?

How does it work ?

A

used to see inside things - diagnose broken bones
x-ray radiation is directed to object onto detector plate
brighter bits are where less X-rays got through (bones/metal)
x-rays may cause mutations like cancer

28
Q

How are Gamma rays useful ?

A

gamma rays kill all microbes so useful for sterilising medical equipment and food
it makes the food fresh for longer

29
Q

how can microwaves be dangerous?

A

heat human body tissue internally by increasing vibrations of molecules

30
Q

how can infrared be dangerous?

A

causes skin burns by making surface (skin) molecules vibrate more

31
Q

how can ultraviolet be dangerous?

A

damages surface cells and can cause blindness

is ionising so can knock off electrons, causing cell mutation (cancer)

32
Q

how can gamma rays be dangerous?

A

ionising and can penetrate far into the body so cause cell mutation, leading to tissue damage and cancer

33
Q

state the law of reflection

A

angle of incidence = angle of reflection

34
Q

look at ray diagrams

A

page 36

35
Q

(Snell’s law) refractive index (n) =

A

sin i / sin r

36
Q

describe the experiment to find refractive index of a glass block

A

draw around a rectangular block on paper and shine light at an angle
trace incident and emergent rays and draw refracted ray
(with normal) measure angle i and r
use snell’s law

37
Q

if the angle i is less than the critical angle then…

A

most of light passes out and only some is reflected internally

38
Q

if the angle i is equal to the critical angle then…

A

emerging ray comes out along the surface and quite a lot is reflected internally

39
Q

if the angle i is more than the critical angle then…

A

no light comes out and all is internally reflected (this is called total internal reflection)

40
Q

sin C =

A

1 / n

41
Q

How do optical fibres work?

A

coating inside has a lower refractive index than the central core so that signals passing through hit the core-cladding boundary at angles higher than C so light is always totally internally reflected

42
Q

describe analogue signals

A

can take any value within its range

the amplitude and frequency can vary continuously

43
Q

describe digital signals

A

can only take two values (on/off or 1/0)

e.g. you can send data along optical fibres as light pulses

44
Q

what are the advantages of digital over analogue ?

A

when digital is amplified, interference/noise is ignored, so signal remains high quality
quantisation works better with digital
can transmit multiple signals at the same time

45
Q

what is interference ?

A

when 2 or more waves of a similar frequency meet and create one combined signal with a new amplitude

46
Q

what is quantisation ?

A

rounding multiple values to a smaller set to pack more information into the same amount of space (signal)

47
Q

what is the frequency range humans can hear sounds ?

A

20 Hz and 20,000 Hz

48
Q

what quickens the speed of sound?

A

a denser medium as sound is caused by vibrating particles (so travel fastest in solids)

49
Q

sound waves can be…

A

diffracted, reflected, refracted (and absorbed (curtains and carpets))

50
Q

what is an oscilloscope ?

A

device that displays sound waves and measures their properties

51
Q

what properties on the oscilloscope effects volume?

A

amplitude

greater amplitude means more energy and louder sound

52
Q

how does frequency effect sound waves?

A

changes the pitch, higher frequency (more vibrations) means high - pitched and low frequency means low - pitched

Physics by Thaidz (7 decks)

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