waves Flashcards
1
Q
transverse waves examples
A
- ripples
- S waves
- electromagnetic
2
Q
longitudinal waves examples
A
- sound waves
- P waves
- pressure waves
3
Q
properties of transverse waves
A
- oscillations perpendicular to direction of energy transfer
- can go through vacuum
- can go through solids
- can ONLY travel on surface of liquids
- CAN NOT travel through liquids or gases
4
Q
properties of longitudinal waves
A
- oscillations parallel to direction of energy transfer
- CAN NOT go through vacuum
- can go through solids, liquids and gases
5
Q
what is the ampiltude in waves?
A
Maximun displacement of a point on a wave away from its undisturbed position
6
Q
what is the wavelength in waves?
A
distance from one point on wave to the equivalent point on the adjacent wave
7
Q
what is the frequency in waves?
and unit?
A
number of waves passing a point each second
Hz
8
Q
what is the period in waves?
and unit?
A
time for 1 wave to pass a point
s
9
Q
what is the symbol for wavelength?
A
λ
lambda
10
Q
what are the sections of longitudinal waves
A
- compressions- where the particles are close together
- rarefractions- particles further apart
11
Q
what is the wave speed in waves?
2 definitions
A
speed at which energy is transferred/ at which waves moves through a medium
12
Q
describe an experiment to determine speed of sound waves
A
- 2 people at a measured distance
- person A has cymbals
- person B has a timer
- person B starts timer when sees A play cymbals and stops when heard
- distance/time
13
Q
describe an experiment to determine speed of ripples
A
- 2 people at measured distance by body of water
- person A has timer
- person B creates ripples
- person A times how long it took ro the ripples to reach them
- distance/time
14
Q
what do waves transfer and does the medium move with it?
A
energy
and no
15
Q
when there are more molecules in longitudinal wave…
eg sound waves
A
wave is faster
therefore fastes in solids
16
Q
when sound waves travel from a more dense area to less dense
what happens to the
- wavelength
- frequency
- velocity
A
- wavelength decreases
- frequecy stays same
- velocity decreases
17
Q
when frequency increases
- velocity
- period
- wavelength
A
velocity increases
period decreases
wavelength increase
18
Q
what can happen to a wave when it hits a boundary?
A
- reflected
- transmitted
- absorbed
19
Q
angle of incidence to angle of reflection
A
equal
20
Q
why is the amplitude of waves lower when transmitted
A
some energy is absorbed
21
Q
why do we see a specific colour
eg. kaeya’s hair as blue
A
the blue is refracted
all other colours absorbed
22
Q
what are sound waves and how do they move
A
longitudinal
vibrations of molecules
23
Q
how are soundwaves converted to sound in our ears?
A
- hits eardrumm and causes it to vibrate
- nerve cells transmit this to the brain where we get the sensation of sound
24
Q
why are soundwaves only converted to sound over a limited range of frequencies?
and what is the range of… ykyk
A
normal human hearing is only from 20Hz -> 20kHz
25
how do ultrasounds work?
- frequency higher than human hearing <20kHz
- they partially reflect off a boundary
- time taken for reflection to reach detecor can be used to determine distance
26
what are ultrasounds used for and how?
- medical- internal orgamns & foetus
- industrial imaging- hidden defects
27
how do you wokout distance from an ultrasound?
speed x time DIVIDED BY 2
28
what are seismic waves produced from?
earthquakes
29
P waves vs S waves
P waves- longitudinal- solids & liquds
S waves- tranSverse- ONLY solids
30
how do seismic waves provide evidence for internal of the Earth where they cannot reach?
after earthquake- seismic waves are detected in different countries
- S waves only found on same side, not passed through middle which tells us that the mantle is solid, but has a liquid core
- P waves are found passed through centre but not in certain areas due to refraction in the liquid core, however sometimes found in those shadow areas- meaning inner core is a solid
- as P waves are faster in solids than liquids
31
what is echo sounding?
high freuqnecy sound wabes to detect objets in deep water amd measure water depth- similar to ultrasound
32
what are electrocmagnetic waves?
what are some properties
**transverse waves** that **transfer energy** from the **source of the waves to an absorber**
- travel through vacuum
- same speed in vacuum and air
- form a continous spectrum- unclear where each waves are defined
33
as you go left to right in EM spectrum
what happens to the:
- wavelengths
- frequencies
- energy
- wavelengths decrease- get shorter
- frequencies increase
- energy increases
34
from left to right on EM spectrum- what are the groups of waves?
1. radiowaves
2. microwaves
3. infrared
4. visible light- red -> violet
5. ultraviolet
6. x-rays
7. gamma rays
35
what is the only part of EM spectrum that is visible to the human eye?
visibe light
36
the EM waves that are higher energy compared to the lower energy
they are highly ionising and much more harmful to cells & tissues
37
from red -> violet, what are the wavelengths and frequencies?
wavelengths decrease
frequencies increase
38
how do microwaves work?
microwaves are absorbed by the water molecules in the food- increasing the energy- increasing the heat
transfer energy by radiation to thermal energy store
39
what is refraction and what happens at the normal line?
- change in speed of waves causing change in direction
- slowing down- towards normal
- speeding up- away from normal
- following normal- doenst change direction only speed
40
why do EM waves refract?
due to difference in velocity of waves in different substances
41
when an atom absorbs EM waves- what happens to the electrons?
the electron goes up energy shells- increase in energy
42
when an atom emits EM waves- what happens to the electrons?
goes down energy shells- loss in energy
43
where are gamma rays emitted from?
the nucleus
44
what are the risks of Ultraviolet waves, x-rays waves, gamma waves
UV- skin cancer, age prematurely
X-rays & Gamma- can cause mutatiom of genes- increasing risk of cancer
^ ionising radiation which knock electrons off atoms when absorbed
45
what is radiation dose
measure of risk of harm resulting from exposure of the body to radiation
Sieverts Sv
46
how can radiowaves be produced?
by oscillations in electrical circuits
47
what happens when radiowaves are absorbed?
can create an alternating current with same frequency
alternating currents have oscillations
48
uses of radiowaves
- transmit radio
- transmit terrestrial TV signals (not satellite or cable- aerial instead)
- , they can travel long distances due to reflecting of ionsphere
- longer wavelength radiowaves can spred out between hills
49
speed of EM waves
3 x 10^8 m/s
50
uses of microwaves
- heating food
- communications to satellites
- ^ can pass through ionsphere
51
uses of infrared
- electrical heaters
- cooking food in ovens
- infrared cameras
- ^ energy of infrared easilty absobed by surface of objects
52
uses of visible light
- fibre optic communications
- ^ telephone and cable TV signals
- ^ short wavelengths- meaning more information transferred
53
uses of ultraviolet
- energy efficient light bulbs
- ^ shorter wavelength than light- more energy- energy is absorvbed by internal surafe of bulb- converted to visible light
- sun tanning
54
uses of x-rays & gamma rays
- medical imaging
- ^ highly penetrating- can pass through body tissues
- ^ x-rays absorbed by bones, gamma- detect cancer
- medical treatments- cancer
55
specular reflection
on a smooth surface
single direction
produces an image
56
diffuse reflection
on rough surface
scattered
no image produed
57
how do colours filters work?
absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colours)
transmitting the specific colour
58
what happens to the parallell waves of light passing through convex lens
they are converge to a specific focus- principal focus (F)
59
what is the focal length
distance between the lens and principal focus
60
if an image is more than 2 focal length away from convex lens, what image is produced?
- diminished
- inverted
- real
61
if an image is between 2 and 1 focal lengths from convex lens, what image is produced?
- magnified
- inverted
- real
62
if an image is less than 1 focal length away from convex lens, what image is produced?
- magnified
- upright
- virtual
63
virtual vs real
real is when the rays meet and therefore can produce an image
64
when is the only time a convex lens will produce a virtual image?
magnifying glass
65
what happens to the parallel rays passing through concave lens?
they diverge, and the principal focus is found from the point the diverging ways came from (dotted line back)
66
what image is always produced in concave lenses?
virtual
67
what is the perfect black body?
an object that absorbs all of the radiation incident on iit. It doesn't reflect or transmit. Also a good emitter as itis a good absorber.
68
the hotter the object...
thermal radiation
amount of thermal radiation it emits increases
therefore wavelngth dectreases- more energy emitted
higher temperature
69
what does the colour of an opaque object depend on?
which wavelenghs of visible light are more strongly reflected
70
why does an object appear:
- white?
- black?
- transparent?
- transculent
- white reflected all wavelengths of visible light equally
- black absorbed all wavelengths of visible light
- transparent transmits all wavelengths of visible light
- transculent transmits all wavelength of visible light but is scattered
71
if an object is warmer than its surroundings, what happens to the radation emitted/absorbed?
emits more than it absorbs
72
when an object is at a constant temperature
absorbing radiation at same rate emitting- equillibrium
73
temperature of the Earth interms of radiation
- Sun emits short wavelengths
- clouds reflect some, but most gets absorbed by Earth- increasing temp (higher energy)
- Earth emits infrared back to space
- some energy trapped by greenhouse gases- causing Earth to be hotter
74
how do cloud coverage affect Earth's temperature
they can reflect the infrared Earth emitted back to Earth- making it hotter
