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BMAT Physics > Waves > Flashcards

Waves Flashcards

(62 cards)

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1
Q

wave definition

A

disturbances that transmit energy from one place to another without transferring matter

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2
Q

propagation direction definition

A

direction of travel of a wave

direction energy is transported

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3
Q

longitudinal wave definition

A

disturbance cause by wave is felt in propagation direction

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4
Q

transverse wave definition

A

disturbance caused by wave felt perpendicular to propagation direction

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5
Q

amplitude definition

A

A

maximum displacement of a wave from resting point

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6
Q

frequency definition

A

f
number of waves passing a point per second
measured in Hz

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7
Q

wavelength definition

A

lambda
length of full cycle of a wave
distance between the same points on 2 waves

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8
Q

shape of transverse waves

A

peaks and troughs above and below equilibrium

oscillated perpendicular to propagation direction

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9
Q

examples of transverse waves

A

EM waves
waves on guitar string
S-waves

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10
Q

shape of longitudinal waves

A

vibrates in propagation direction

areas of high density (compression) as oscillating particles forced close together, areas of low density (rarefraction)

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11
Q

examples of longitudinal waves

A

sound waves

P-waves

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12
Q

S-waves vs P-waves

A

both mechanical waves
S-waves travel transverse through solid rock only, slower
P-waves travel longitudinal through solid + liquid rock, faster

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13
Q

wave equation

A 
wave speed(m/s) = frequency(Hz) x wave length(metres)
v = f  x lambda
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14
Q

period definition and formula

A

T
how long it takes to complete 1 oscillation
T = 1/f

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15
Q

reflection definition

A

change in direction of a wave without change of speed, wavelength or frequency

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16
Q

law of reflection

A

angle of reflection = angle of incidence

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17
Q

refraction definition

A

change in direction of a wave as it travels from one medium to another with a different refractive index
greater difference in refractive index = greater change in speed and direction

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18
Q

how refraction occurs

A

waves meet new medium at angle to boundary (not perpendicular to boundary or else no change in direction, just less wave speed and wavelength)
enters medium w/ greater refractive index = bends toward normal
enters medium w/ lower refractive index = bends away from normal

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19
Q

how dispersion occurs and why

A

white light shone through a prism at an angle to the boundary
different wave lengths refracted by different amounts
splits into difference colours

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20
Q

sound type of wave

A

longitudinal

mechanical

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21
Q

sound features

A

requires medium to travel through
travels fastest through denser (solid) mediums
causes air molecules to vibrate

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22
Q

pitch

A

depends on frequency of sound waves
high-freq sound wave = high pitch, short wavelength
low-freq sound wave = low pitch, long wavelength

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23
Q

range of ultrasound

A

> 20kHz

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24
Q

range of infrasound

A

< 20Hz

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25
volume
depends on amplitude of sound waves
26
why pitch and volume are independent
frequency and amplitude are independent
27
echo definition
delayed reflections one hears after an initial sound has passed
28
how echoes occur
noise made some of sound waves travels first to the ear and registered by brain some of sound waves travels away from source, reflected off surface and heard by ear and registered by brain with time delay
29
why sound waves change in direction due to refraction hard to hear
sound waves spread out too much
30
electromagnetic waves summary
all transverse waves spectrum divided into 7 regions based on wavelength/frequency all have same speed
31
speed of light in vacuum
3x10ms^-1
32
radio waves defined as
longest wavelength of EM spectrum | wavelength > 10cm
33
radio waves main uses
broadcasting communication e.g. radio/TV/mobile phone signals
34
shortwave radio signals length + uses
wavelength: 10-100m long distance communication (TV, FM) signal bounces off ionosphere due to short wavelength
35
longwave radio length and uses
wavelength: 1-10km | travel long distances because can diffract around Earth’s curved surface
36
diffraction definition
involved change in direction of waves as they pass through an opening or around a barrier in their path results in direction of wave changing + wave spreading out perpendicular to propagation direction + transmitting over greater area
37
order of EM waves (wavelength longest to shortest)
``` radio waves microwaves infrared radiolarian visible light ultraviolet light x-rays gamma rays ```
38
energy, wavelength and frequency
shorter wavelength = faster frequency (due to wave equation) | faster frequency = more energy
39
microwaves in TV
transmitters produce microwaves able to pass through Earth’s atmosphere to satellites in space bounces signal down to desired locations, picked up by satellite dish
40
microwaves in mobile phone signals
signal from phone travels to nearest transmitter as microwaves then to other phones
41
microwaves in cooking food
penetrates few centimetres into food before being absorbed by water molecules water molecules vibrate (heats up), cooks food by conduction and convection
42
microwaves dangers
frequency when used in communication too low to damage tissues can cause internal hearing of body tissues with higher frequencies, causes burns
43
how microwave ovens are safe
metal cases | screens over glass doors reflects and absorbs microwaves to prevent them from escaping
44
infrared radiation features
wavelength: 700nm to 1mm
45
infrared wavelength
700nm to 1mm
46
how IR cameras work
good for producing images in the absence of visible light detect IR to produce an image more IR emitter = warmer region
47
uses of IR
``` monitoring temperatures heating food security cameras night-vision automatic doors short distance communication (remote controls) optical fibres ```
48
how optical fibres work
thin rods of high quality glass transmit information as infrared signals repeatedly and rapidly reflects infrared from one end to the other
49
greenhouse effect
Sun’s rays enters Earth’ atmosphere some pass through outer atmosphere, some reflected back out into space rays reach surface, some partially reflected or partially absorbed depending on object they incident on surface of Earth radiates IR back into space greenhouse gases in atmosphere absorb some of IR instead of reflecting it back to space gases conduct, convect, radiate heat to surroundings
50
greenhouse gases examples
carbon dioxide water vapour methane
51
visible light wavelength
300nm to 700nm
52
how sight works
visible light reflected off object into eye lens refracts visible light focused onto retina retina sends messages to brain via optic nerve to be interpreted
53
what happens if intensity of incident light too high
if intensity of incidence light too high, causes blindness
54
UV light wavelength
100nm to 400nm
55
why we tan
skin absorbs UV light | turns darker to absorb more UV light to prevent it from reaching deeper tissue
56
UV light uses
detect forged bank notes (real ones have fluorescent ink) security pens treatment of skin conditions, sterilise medical equipment fluorescent lamps
57
dangers of overexposure to UV light
eye problems | damage DNA, causes cancer
58
X-rays wavelength
0.01nm to 10nm
59
X-rays uses
``` investigate internal structure of objects passes through less dense objects, absorbed by denser objects detect bone fractures airport security (scan luggage) ```
60
gamma rays wavelength
smallest wavelength | highest energy
61
gamma rays uses
sterilise food+medical equipment | diagnosis + treatment of cancer
62
X-rays/gamma rays dangers
high ionising ability can damage greater number of cells can cause tissue damage and cancer

BMAT Physics (7 decks)

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