Waves Flashcards
eg transverse waves
ripples on surface of water
eg longitudinal waves
sound waves travelling in air
what do waves do
transfer energy from one place to another
what type of energy do the ripples on water transfer
kinetic energy
what are the up and down movements of waves called
ocsillations
describe transverse wave
ocsillations are perpendicular to direction of energy transfer
what does ‘perpendicular’ mean
at right angles
how do sound waves travel
as particles in the air move from side to side
what are ‘compressions ‘ in air
regions where the air particles are very close tgether
what comes between compressions
rarefactions
what are rarefactions
regions where air is spaced out
describe longitudinal wave
oscillations parallel to direction of energy transfer
what do all longitudinal waves require to travel in
a medium, eg
air
liquid
solid
what is different between transverse and longitudinal in terms of needing a medium in order to travel
NOT ALL transverse need a medium to travel in
ALL longitudinal waves need a medium
what is travelling in terms of ripples on a water surface
the wave is travelling, not the water
what is travelling in terms of sound waves in air
the wave is travelling, not the air
what can a slinky be used to represent
transverse waves
(eg ripples on surface of water)
what does the red dot in the slinky represent
-a single point (eg a water molecule)
how does the slinky example prove that the wave and not
the water / air itself travels.
when wave travels through/ slinky is moved,
the dot oscillates up and down
but doesn’t travel along the medium
what happens when longitudinal waves are sent along slinky
red dot oscillates from side to side
doesn’t travel through medium
what does red dot in slinky, in transverse wave represent
particle of air
what is amplitude- define it
the maximum displacement of a point
on a wave away from its undisturbed position.
where is the undisturbed position
the points horizontally along the centre where the wave isn’t moving
define wavelength
distance from a point on one wave
to the equivalent point on the adjacent wave
where can a wavelength be on a longitudinal wave
at any point,
eg middle or bottom
(just needs to be the equivalent point on the next wave)
symbol for wavelength
greek letter lamda
λ
how to measure wavelength on longitudinal wave
from one compression to next compression
from one rarefaction to next rarefaction
define frequency
number of waves passing point each second
unit for frequency
Hz
one Hz is equal to……
one wave per second
what does period of a wave mean
time in seconds for one wave to pass a point
unit for period
seconds
define wave speed
speed at which wave moves through the medium
equation for wavespeed is:
v = f λ
what do the symbols represent
wavespeed= frequency x wavelength
what is wavespeed (v) measured in
m/s
what is frequency (f) measured in
Hz
what is wavelength λ measured in
m
describe a method to measure the speed of sound waves in
air
5 points
-2 people stand 500 m apart
-person A has symbols
person B has timer
-B starts timing when she sees A clash cymbals together
-B stops timing when she hears sound of cymbals clashing
-Do equation-
speed of sound waves=
Distance travelled / time taken
the 2 problems with method of measuring speed of sound waves
- describe what you mean
- everyone has different reaction time
takes fraction of a second between
seeing cymbals & starting timer and also between hearing sound and stopping timer
- time btwn seeing cymbals clash and hearing them is short
means its difficult to press timer at correct time
how to reduce error of different reaction times
-large number of observers
use all results, discard anomalous results, find mean
how to reduce problem of short time between hearing + seeing
increase distance between person A and B
what is a ripple tank used for
to observe the features of water waves
describe what a ripple tank looks like
shallow tray of water
a vibrating bar in the water
bar is connected to power pack
what happens when the bar vibrates in the water
it creates waves across the surface of the water
what is above and what is below the ripple tank
above is a lamp
below is sheet of WHITE paper
what happens when light shines through the water
it creates an image of the waves on the paper
what are we using the ripple tank to measure x3
wavelength
frequency
speed
of waves
how are we going to video the waves shown on the paper and why in this way
using a mobile phone
we can freeze the video
play video at different speeds
how do you measure wavelength from the waves reflected on the paper
5 points
put the ruler next to paper
freeze image of waves
measure distance of 10 wavelengths
divide by 10 for 1 wavelength
turn from cm into metres
how do you measure frequency of the waves reflected on the paper
put timer next to paper
play video in slow motion
count number of waves passing a point in 10 seconds
divide answer by 10 to get frequency
2 ways to work out speed of the waves reflected on the paper
-use equation: v = f λ
(do frequency x wavelength)
OR
-choose a wave
-measure the time it takes to move the length of tank
- then do: speed = distance/time
one issue that arises as there are 2 ways to work out speed of the waves reflected on the paper
why this issue arises
-may get slightly different results
-due to measurement errors eg timing
list all the components / parts of the set up to measure frequency/wavelength/speed of waves in a solid in order
signal generator
vibration generator
string
wooden bridge
pulley on a clamp
mass
describe the apparatus used to measure frequency/ wavelength / speed of waves in a solid
-string with one end attached to vibration generator
-hanging mass at other end of string
-vibrator generator attached to signal generator
what does the mass at the end of the string do
keeps string taut
what does the signal generator let us do
change the frequency of vibration of the string
what happens when we turn on the power in the apparatus used to asses waves in a solid
the string vibrates
when, where, why do we get a standing wave
in the string
at certain frequencies
due to resonance
give an everyday example of resonance
stringed musical instruments eg guitar.
what do we use to measure the wavelength of the standing wave
a ruler
how do we measure the wavelength ( from where to where ) in the RP for assessing waves in a solid
measure length of standing wave from wooden bridge to vibration generator
turn from cm to m
how do we find out frequency for waves in a solid
read the frequency generator
how do we calculate speed of waves in a solid
calculate speed of wave by: v = f λ
what happens if we increase the frequency through a standing wave
wavelength increases
how would you calculate the wavelength of a wave with 3 half wavelengths in the RP for waves through a solid
measure distance from wooden bridge to vibration generator
(eg 0.125 metres)
divide this length by number of half wavelengths
(eg. 0.125m / 3)
then times answer by 2
(eg… ( 0.125m/3) x 2) =0.143m
In the RP for waves in a solid, what does the wave speed of the string depend on
tautness of string
&
mass/cm
when wave hits boundary with different material, 3 things can happen….
waves are either:
transmitted
absorbed
reflected
describe what it means when a wave is transmitted
passing through the material doesn’t change the wave
what could potentially happen when a wave is transmitted
-refraction
(waves can change direction)
what happens when a wave is absorbed
energy of wave absorbed
wave wont pass through material
what is meant when wave is reflected
wave reflected off materials surface
whether transmittion, reflection, absorbtion happens depends on….
on the material
on the wavelength
describe initial parts of ray diagram for reflection
mirror line- horizontal/ vertical line, dashed along one side
incident ray- angled straight line, touches bottom of mirror line
what parts do you add on to your ray diagram for reflection
normal- draw dotted line at right angles to surface of mirror
angle of incidence- measure angle between incident ray and normal
angle of reflection- measure same angle ( of incidence) on other side of the normal
reflected ray- angled straight line going downwards from normal, with same angle as angle of incidence
( basically your angle and ray of incidence is reflected on the other side by the normal)
key fact for reflection in all waves
angle of reflection= angle of incidence
how to use a ray diagram to workout where an image will appear in the mirror if an object is infront of a mirror
-draw incident ray from object to mirror
-draw normal at right angles to mirror’s surface
-draw reflected ray
-draw #2 normal higher up , #2 incident ray from object to mirror #2 reflected ray
-extend both reflected rays so they meet at a point
-that point= position of image
what must you remember when drawing rays
the arrows showing direction
what things used to investigate reflection and refraction
ray box
lens
slit
what do the ray box, lens and slit produce when used together
narrow ray of light
hazard of ray box, and a control for this
ray boxes get hot
switch off when not in use
what alternative can be used to a ray box, why don’t we use this instead
a laser, dangerous
RP 9
Part 1
how to make reflected ray and refracted ray- up till transmitted ray
-on A3 paper draw straight line down center
use ruler
- Normal- ( line at right angle )
use protractor- label N
-place glass block against first line so normal goes through center
-draw around glass block
-turn off all lights
-incident ray- use ray block so ray hits block at normal
-adjust ray box - change angle of incidence till reflected ray & transmitted ray visible
how do we draw the normal in when making rays of reflection and refraction
use protractor to draw line at right angles to initial line
what do we label the normal when making rays of reflection and refraction
N
how do we make the incident ray when making rays of reflection and refraction
use ray block so ray hits block at normal
when do we stop adjusting the ray block
when reflected ray and transmitted ray are visible
what is the transmitted ray
ray leaving block from opposite side
RP 9
part 2
what do we do once we have the transmitted ray and the ray of reflection when making rays of reflection and refraction
( up to line through glass block)
-use crosses to mark path of all three rays
( transmitted, reflected, incidence)
-turn on lights
-switch off ray box
- remove glass block
-draw all rays ( use the crosses )
- draw line to show path of transmitted ray through glass block
how many x’s do we put on each ray when making rays of reflection and refraction
1 on reflected
1 on incident
2 on transmitted
RP 9
part 3
what do we do once we’ve drawn the line showing the path of transmitted ray through the glass block- when making rays of reflection and refraction
use protractor to measure important angles
do whole experiment again- use different material
RP 9 - making rays of reflection and refraction
what are the important angles to measure
reflection
incidence
refraction
where is the angle of refraction
angle between normal and the path of the transmitted ray through the block
what other material can u use when repeating RP 9
( making rays of reflection and refraction)
perspex (plastic)
what will you find when you repeat RP 9 with different material + what materials
angle of incidence and reflection are the same in glass and Perspex
why does angle of incidence and reflection stay same in glass and Perspex in RP 9
angles of incidence and reflection X depend on material
what angle will change when repeating RP 9 with Perspex instead of glass + why
angle of refraction ,
as angle of refractions different for different materials
is sound longitudinal or transverse wave
longitudinal
what happens when sound waves move through air
air particles vibrate from side to side
can air particles vibrations move from one medium to another
yes
when ….. waves move through air, air particles vibrate from ….. to ….. these vibrations can move from one ……… to ……..
eg from …. to ….
when sound waves move through air, air particles vibrate from side to side. these vibrations can move from one medium to another
eg from air to solid.
what is one key part of a microphone
paper cone
what happens when sound waves hit the cone in a microphone
cone vibrates
when the paper cone vibrates, what does the microphone do
microphone converts vibrations into electric signals
describe movement of sound waves into ear
sound waves funneled into ear where they hit eardrum
what is the ear drum
thin membrane
what do the sound waves in the ear cause
cause ear drum &
other parts of inner ear
vibrate
causing sound
sound waves in air trigger
vibrations in solids
vibrations in solids can only be triggered by sound waves at…..
limited range of frequencies
what is range of normal human hearing
20-20,000 Hz
what is 20,000 Hz in kHz
20,000 Hz = 20 KHz
what potentially happens if frequency of sound wave is outside of 20Hz-20,000Hz
eardrum not vibrate
what can happen when wave moves from 1 medium to another
speed can change
give example of a wave slower in 1 medium compared to another
sound waves-
travel faster in solids than in gases
why do sound waves travel faster in solids than gas
particles closer together in solid
vibrations pass more easily (from particle to particle)
what is changed when wavespeed changes
wavelength
when wavespeed increases, what happens to wavelength
increases
when a wave changes medium, the frequency
does not change
why does frequency not change when wave changes medium
waves would have to be created and destroyed at the boundary, thats’ not possible
how can we view features of sound waves
connect microphone to cathode ray oscilloscope
what is issue with cathode ray oscilloscope
represents sound waves as transverse
(sound waves are longitudinal)
if a sound has high frequency, it has a
high pitch
how to know if a sound has low pitch
if it has low frequency
if a sound has a small amplitude, it has a
quiet sound
how to know if a sound is loud from looking at cathode ray oscilloscope
if it has large amplitude
high frequency sound wave means
high pitch
large amplitude sound wave means
loud sound
low frequency soundwave means
low pitch
small amplitude sound wave means
quiet sound
if a sound is high pitched, it will have a
high frequency
if a sound is loud it will have a
large amplitude
if a sound is low pitched it will have a
low frequency
if a sound is quiet it will have a
small amplitude
sound waves can only move through a …….. for example through …….
medium
eg- solid
why can sound waves only move through a medium
because sound waves move by particles vibrating
where can sound waves not pass through, why
cant pass through vacuum
no particles
can sound waves be reflected
yas
what is a reflected sound wave called
echo
what are ultrasound waves
waves with frequency higher than upper limit of human hearing
what is upper limit of human hearing
20,000Hz
what happens to ultrasound waves at the boundary between 2 different densities
ultrasound waves partially reflect
a device that gives out + detects ultrasound waves
ultrasound probe
if we know the time taken for ultrasound pulse to leave probe, bounce off kidney and then be detected by probe, we can calculate……
distance between probe and kidney
the distance between the detector and the boundary can be calculated if you know
time taken for ultrasound reflections to be detected by the detector
ultrasounds can be used to for……
producing images of internal organ
producing images of foetus
industrial imaging
what must an organ have/ not have to be able to produce an image of it using ultrasound
organ must not be surrounded by bone
what is safer:
ultrasound or x-ray
ultrasound
why is ultrasound safer than x-ray
2 points
doesnt cause mutations
doesnt increase cancer risk
example of ultrasound being used for industrial imaging
ultrasound used to scan a pipe
why would ultrasound be used to scan a pipe
2 reasons
-detect hidden defects
-problems with a weld
how can we use ultrasound to work out distance
use equation:
(distance = speed x time)
what is distance measured in
metres
what is speed measured in
m/s
what is time measured in
seconds
ship uses ultrasound to measure distance to seabed.
ultrasound pulse is emitted
it takes 1.2 seconds for reflected pulse to return to ship
calculate depth of sea bed
speed of ultrasound in water is 1600 m/s
s=vxt
s= 1600 x 1.2
distance = 1920 meters
1920/2 =960 metres
why sometimes divide by 2 when working out distance using ultrasound wave
because your answer could be from ship to seabed and then seabed back to ship
what is outer layer of earth made of- describe it
solid crust- very thin
what comes under crust
mantle
what is max depth of the solid outer crust
50 km+
is mantle considered solid, liquid , gas
solid
what parts of mantle can flow very slowly
parts of upper mantle
what comes under mantle
outer core
is outer core solid, liquid. gas
liquid
what comes under outer core
inner core
is inner core solid, liquid,gas
solid
there is ….. way for scientists to directly ….. the ……. of earth
there is no way for scientists to directly observe the interior of the earth
deepest mines go ……… into the crust
a few km
how do scientist know the internal structure of earth
due to earth quakes
why do earthquakes happen
sudden movement between tectonic plates and earths crust
the sudden movement between tectonic plates causes….
seismic waves
what do seismic waves do
carry energy away from the earthquake and pass through the earth
how are seismic waves detected
by seismometers in different countries
info about the interior of the earth comes from…..
the pattern of waves on the seismometer
2 main types of seismic waves
p waves
s waves
e p waves or s waves longitudinal
p waves
e p waves or s waves longitudinal
p waves
e p waves or s waves longitudinal
p waves
e p waves or s waves longitudinal
p waves
are p waves or s waves longitudinal
choose one.
p waves
p waves can pass through
solids and liquids
which travel faster, p or s waves
p waves
are s waves longitudinal or transverse
transverse
s waves pass through
solids only
describe pathway of s waves through the earth
curved paths
(start at point,
curve outwards,
go through crust and mantle)
why do seismic (s) waves travel in curved paths
due to density changes in the earth
what do you call the part of the earth where no s waves can be detected
s wave shadow zone
why is the s wave shadow zone created
because s waves can’t pass through liquid
(the waves turning point is when it reaches liquid )
s waves cant travel through liquids, this causes the s wave shadow zone. Scientists used this info to work out that…..
the earth must contain a liquid core
where can p waves be detected on the earths surface
https://images.app.goo.gl/cpvbFLuUXMB7qTsYA
p waves can be detected around most of the earth
except 2 parts opposite each other on north and south of earth
what do we call the places where p waves cannot be detected
p wave shadow zones
what is the reason for p wave shadow zones
p waves travel faster in solids than liquid
what happens when p waves enter liquid outer core
p waves slow down
causing refraction ( change in direction)
2 times p waves refract in the earths interior
when they leave the outer core
when they enter the outer core
p waves refract when entering and leaving the outer core. What does this confirm
that the outer core is a liquid
p waves move slower through liquid, that why they refract in outer core
what can be detected in the p wave shadow zone
faint p waves
faint p waves can be detected in the p wave shadow zone. this is used by scientists to prove that…..
the earth contains a solid inner core
scientists have measured the ………waves of ……… of ………..
scientists have measured the seismic waves of thousands of earthquakes
scientists have measured the seismic waves of thousands of earthquakes. They’ve used these to work out
thickness of crust, mantle, outer, inner cores
light is an example of an ……………. wave
electromagnetic
are electromagnetic waves longitudinal or transverse
transverse
what do electromagnetic waves do
transfer energy from source of wave to absorber
what do electromagnetic waves in a microwave oven do - give examples
transfer energy from the source- the oven
to the absorber-
the food
what is the electromagnetic wave in the microwave oven
microwave
what is the electromagnetic wave in solar panels
light waves
what do electromagnetic waves in a solar panel do
transfer energy from the source-
the sun
to the absorber-
solar panels
what happens to white light passed through a prism
it splits into a spectrum
what type of light splits into a spectrum when passed through a prism
white light
each colour of light has a different..,….. and ………
wavelength and frequency
order of colour spectrum
red
orange
yellow
green
blue
indigo
violet
Roy. G. Biv
describe wavelength of waves on red end of spectrum
longer wavelength
describe frequency of waves on red end of spectrum
lower frequency
describe wavelength of waves on violet end of spectrum
shorter wavelength
describe frequency of waves on violet end of spectrum
higher frequency
visible light forms a …… part of the electromagnetic spectrum
small part
visible light is the only part of the spectrum that
can be detected by the human eye
state the electromagnetic spectrum from low frequency to high frequency
radio
microwaves
infrared
visible light
ultra violet
x rays
gamma rays
what is the mnemonic to remember electromagnetic spectrum
raging
Martians
invaded
venus
using
X-ray
guns
what happens to frequency from radio to gamma rays
frequency increases from radio to gamma rays
what happens to wavelength from radio to gamma rays
wavelength decreases from radio to gamma rays
scientists say the electromagnetic spectrum is a ……
continuous spectrum
what does a continuous spectrum mean
the cut off point between one type of wave and another is not always clear
do electromagnetic waves need a a medium to travel in ?
no
true or false:
electromagnetic waves CAN NOT travel through a vacuum
false,
electromagnetic waves CAN travel through a vacuum
what can you say about the speed of electromagnetic waves in a vacuum
all electromagnetic waves travel at the SAME speed in a vacuum
what is the speed of all electromagnetic waves in a vacuum-
300,000 000 m/s
…,….. materials absorb, ………. or reflect ………… waves
different materials absorb, transmit or reflect electromagnetic waves.
whether an electromagnetic wave is absorbed, transmitted or reflected depends on ……..
the wavelength
describe how different materials act differently to the same wave in a microwave oven
microwaves are absorbed by food- which contain water particles
microwaves are reflected from metals
describe how different surfaces act differently to light waves
light rays absorbed by black surfaces
light rays reflected from shiny , metallic surfaces
what happens to light as it passes through water
light appears to change direction as it passes through water
light appears to change direction as it passes through water. This is due to …….
refraction
when waves change speed, they can also change……
direction
when does the speed of a wave change
when it moves from one medium to another
what is used to illustrate how waves change direction when changing speed (moving from one medium to another)
a ray diagram
what happens to light when it passes from air into glass and what does this in turn cause
velocity of light decreases. This causes the direction of wave to change
what does ray diagram of light ray from air to glass look like
normal at right angle to surface of glass
ray bends towards normal
light ray passes through glass block
when ray passes from glass back to air,
ray bends away from normal
this causes image of object to appear to have shifted position
what happens to light ray as it passes from glass back to air
velocity increases, bends away from normal
why does light ray bend towards normal
because velocity decreases
in a ray diagram…..
there is a normal at a right angle to surface of glass
ray bends towards normal as it slows down
light ray passes through glass block
when ray passes from glass back to air,
ray bends away from normal because it speeds up
what does this cause?
causes image of object to appear to have shifted position
what is the light ray that enters the glass block called
incident ray
what is the light ray that leaves the glass block called
refracted ray
when can refraction happen
2 points
when any wave changes speed
going from one medium to another
what is the one exception when waves enter/ leave a different medium but don’t change direction - refraction doesnt happen
when they enter/ leave at right angles to the surface, along the normal
what diagrams are used to explain refraction
wave front diagrams
a wave front is found in a group of ………. waves travelling ……..
group of identical wave travelling together
what is a wave front
an imaginary line that connects all the same points in a set of waves
can wave fronts only be applied to longitudinal, transvers, or both types of waves?
BOTH
wavefronts make it easier to visualise……
lots of waves moving together
what do we do once we’ve drawn on the wavefronts onto the waves
remove the waves so we just have the wave fronts ( the lines connecting all the same points in a set of waves )
explain what happens to wave fronts travelling at an angle when they go from air to glass
when parts of wavefronts move into glass, those parts slow down
what happens when parts of wave fronts slow down on entering a new medium. why
-their wavelengths get smaller
because those parts of the wavefront move closer together
-waves bend towards the normal
another word for when the waves bend towards the normal
is…
refracting
what happens to wavefronts approaching along the normal into glass
2 points
waves slow down but do not change direction
why do wave fronts approaching glass along the normal not change direction
because the whole wavefront slows down at the same time
why do wavefronts that approach glass not along the normal refract
because some parts of the wavefront slow down first
hot surfaces, like glowing coals, emit……
infrared radiation
can humans see infrared radiation
no
what is a Leslie’s cube used for
to see how much infrared is emitted from different surfaces
how many different surfaces does a leslies cube have
4
name the 4 different surfaces of a leslie’s cube
shiny metallic
shiny black
white
matt black
RP 10 investigate how the amount of infrared radiation radiated by a surface depends on the nature of that surface.
list steps
x3
.fill leslie’s cube with hot water
.point infrared detector at each of 4 different surfaces
.record amount of infrared emitted
important things to remember when recording amount of infrared on each surface of Leslie’s cube
keep same distance between Leslie’s cube and infrared detector
why is keeping the same distance between the Leslie’s cube and infrared detector is important.
makes the measurements repeatable
what surface emitts most infrared
matt black
what surface emits least infrared
shiny metallic
list the 4 materials on the leslie’s cube from which emits most infrared radiation to which emits the least infrared radiation
matt black
shiny black
white
shiny metallic
what can be used to measure infrared radiaition if we don’t have an infrared detector
use a thermometer with the bulb painted black
issue with using a thermometer with a black painted bulb instead of an infrared detector when comparing amount of infrared radiated by different surfaces
2 points
resolution of thermometer lower than infrared detector
the infrared detector is more likely to detect a difference
define resolution
the smallest change that can be detected
describe the equipment needed to measure the absorbance of infra red
by different surfaces
infrared heater,
metal plate on either side
one painted shiny metallic
other painted matt black
drawing pin attached to outer side of each
plate using vaseline
how do you carry out the experiment to investigate how the amount of infrared radiation absorbed depends on nature of surface
turn on the heater (between the metal plates)
start the timer
record time it takes for vaseline to melt + pins to fall
when investigating the amount of infrared radiation absorbed what happens to the metal plates as they absorb infrared
temp of plates increases as they absorb infra red
will the drawing pin fall off the matt black or shiny metallic plate first + why
matt black
because matt black surfaces absorb more infrared than shiny metallic surfaces
what conclusion can be draw from RP 10 investigating how the amount of infrared radiation absorbed or
radiated by a surface depends on the nature of that surface
matt black surfaces are better at absorbing and emitting infrared than shiny metallic surfaces
infrared is reflected from shiny metallic surfaces
what colour light emitted when lithium is heated in a flame
red
when lithium atoms are heated and give out a red light, what type of wave do they emit?
electromagnetic waves
what happens when electromagnetic waves are generated or absorbed over a wide frequency range
changes take place in atoms and nuclei of atoms
what happens inside atoms when they are heated
electrons move from one level to a higher energy level
what happens when an electron moves back to its original energy level after being heated
it generates an electromagnetic wave- (eg. light)
how can an electromagnetic wave be generated
x2
when an electron moves back to its original energy level
a change to the nucleus
where do gamma rays originate from
changes in the nucleus of an atom
where can gamma rays be emitted from
the nucleus of radioactive atoms
when a gamma ray is emitted from the nucleus of an atom it means that the nucleus….
the nucleus has less energy than at the start
what happens when electromagnetic waves are absorbed by atoms + give an example
the atom changes - eg electrons can change energy shells
…….. waves can be emitted and …… over a ……. frequency range from radiowaves to ……….. rays
electromagnetic waves can be emitted and absorbed over a wide frequency range from radio waves to gamma rays
hazards of ultraviolet waves on human tissue x2
increase risk of cancer
cause skin to prematurely age
x-rays and gamma rays are both types of
ionising radiation
what do xrays and gamma rays do to atoms when absorbed
knock electrons off atoms
hazards of x-rays and gamma rays
x2
mutates genes which…
increases risk of cancer
what does the damage caused by radiation depend on
x2
the type of radiation
the dose
what is dose of radiation measured in ???
sieverts (Sv)
millisieverts (mSv)
how can radio waves be produced
when electrons oscillate in electrical circuits
what does oscillate mean
move back and forward
can radio waves be absorbed.
if yes, give example.
if no state why not
yes,
an electrical circuit in an aerial
what happens when radio waves are absorbed by an electrical circuit in an aerial
the electrons in the circuit oscillate
when radio waves are absorbed by an electrical circuit, the electrons in the circuit also oscillate. What is now created
2 points
an alternating current
with the same frequencies as the radio waves
radiation dose is the measure of….
the risk of harm from body exposure to radiation
radiation dose is the measure of….
the risk of harm from body exposure to radiation
radio waves are used to transmit…..
x2
radio &
terrestrial TV signals
what is terrestrial tv
tv received using an aerial
why are radio waves useful
travel long distances before being absorbed
this is
reflect off layer of charged particles in atmosphere
what specifically can longer wavelength radio waves do
spread out between hills
*not on spec, delete if u want *
what is it called when waves can spread out between hills
diffraction
what is a layer of charged particles in the atmosphere called
ionosphere
radio waves can travel long distances around the earth before being absorbed. what is the reason for this
because they reflect off layers of charged particles in atmosphere
uses of microwaves
x2
heat food
communicate with space satelites
why are microwaves used to heat food
most foods contain many water molecules
water molecules absorb energy of microwaves
what does the energy of microwaves cause
the temp of food to increase
why are microwaves used to communicate with satelites in space
because microwaves pass through earths atmosphere without being reflected or refracted
uses of infrared x3
electrical heaters
ovens (cook food)
infrared cameras
why is infrared used in electric heaters and ovens
give an example in terms of heaters
the energy of infrared is easily absorbed by the surface of objects
- infrared from heater absorbed by objects in room
example of what infrared cameras are used for
check for heat loss
use of visible light
fibre optic communications
what are optical fibres
very thin glass strands
what do we do to the optic fibres to carry info
transmit pulses of light down fibres
use these pulses to carry info
what are optical fibres used for
carry telephone signals
carry cable tv signals
does visible light have short or long wavelength.
why is this useful.
short wavelength
it can carry alot of info
uses of ultraviolet light
energy efficient lamps
sun tanning
does ultraviolet light have short or long wavelength
short
what carries more energy, visible light or ultraviolet light?
ultraviolet light
what happens inside an energy efficient light bulb
ultraviolet light is created inside the bulb
-energy of ultraviolet is absorbed by the internal surface of the bulb
-it is converted to visible lightultraviolet light is created inside the bulb
-energy of ultraviolet is absorbed by the internal surface of the bulb
-it is converted to visible light
in an energy efficient bulb,
-ultraviolet light is created inside the bulb
-energy of ultraviolet is absorbed by the internal surface of the bulb
-it is converted to visible light
Why is this good
It requires less energy than a normal light bulb
hazards of ultraviolet light x2
increase risk of skin cancer
premature skin aging
uses of x rays and gamma rays
medical imaging
treatments
example of what x-ray can detect in medical imaging
broken bone
example of what gamma ray can detect in medical imaging
cancers
both x-rays and gamma rays are very ……
penetrative
what does a penetrative wave mean
pass easily through body tissue
why can we see x-rays on x-ray images
because x rays absorbed by bones
example of a medical treatment that x-rays and gamma rays can be used in
to treat cancer
what is the idea of refraction
waves change direction when they change speed, going from one medium to another
describe shape of convex lenses
thicker at centre than edges
what is the symbol for convex lens
straight line down with arrow on both ends
key feature of all lenses
they refract light
what happens to the light ray as it passes into the lens
it bends towards the normal
what happens to the light ray as it passes out of the lens
bends away from normal
when parallel rays of light pass through a convex lens what are the two main things that happen
central ray passes through lens without being refracted
all other rays refract and are focused at a point
why is the central ray not refracted when it enters a convex lens
because this ray passes directly along the normal
when the central ray passes through the lens without being refracted, we say that this ray ……
is passing along the principal axis
-centre of the lens
when parallel rays pass through a convex lens all rays (except central ray) refract and are focus at a point.
what is this point called?
the principle focus
what is the symbol for the principle focus
F
what do you call the distance from the centre of the lens to the principle focus
focal length
does the focal length change with different convex lenses
yes
the focal length depends on
the strength of the lens
when parallel rays pass through a convex lens , which rays meet at the principle focus
all the rays, even the central ray
how to draw ray diagram for convex lens
4 points
what will already be there:
-straight line horizontally- the principle axis
-convex lens symbol going down through centre of principle axis
-place object minimum 2 focal lengths away from lens
-draw diagonal line from top of object through centre of lens- without changing direction
- draw line parallel to pricipal axis from top of object across to lens
-when line hits lens, its refracted through principal focus.
where two lines meet shows top of image
3 key features of the ‘image’ made through a ray diagram
image is diminished
-(smaller than object)
image is inverted
-(upside down)
this is a real image
what is meant when an image is a ‘real image’
2 points
the rays actually meet at a point
if you placed a screen there you would see the image in the screen
what are the properties of the image formed in a ray diagram when object is between one focal length and two focal lengths
magnified image ( larger than object)
inverted
image is real
the properties of an image depend on what
the distance between the object and the lens
3 properties of image if object is more than 2 focal lengths from the lens
diminished
inverted
real
3 properties of image if object is between 1 and 2 focal lengths from the lens
magnified
inverted
real
magnifying glass works when an object is …….
a) between 1 and 2 focal lengths from the lens
b) less than 1 focal length away from the lens
c)more than 2 focal lengths away from the lens
B
if an object is less than 1 focal length away from the lens you could also say that the object is very ……. to the lens
close/near
describe ray diagram for magnifying glasses
-object is between 1 focal length and the lens
-draw line (ray) from top of object through centre of lens- doesn’t change direction
-another line(ray) from top of object, parallel to principle axis
-this line (ray) then passes through principle focus
–rays/lines don’t meet
-draw dotted line to extend rays/lines behind object
-where they meet shows image position
what do the lines we draw in ray diagrams represent
light rays
3 key properties of image formed by ray diagram of magnifying glass
magnifies
not inverted(image same way up as object)
image is virtual
how can you tell that the image formed in a ray diagram of a magnifying glass is virtual
- rays don’t meet at a point
-we could not see this image on a screen
when is the only time that a convex lens produces a virtual image
when it is used as a magnifying glass
what must happen to make a convex lens be used as a magnifying glass
the object is less than 1 focal point away from the lens
unit for magnification
why
no units
its a ratio
magnification = image height / object height
what are the units for height
cm
mm
the image formed by a convex lens can be either……. or……
real
virtual
describe concave lens
thicker at edges than centre
what does a convex lens do in brief
focus parallel rays of light to a point- the principal focus
describe symbol for concave lens
straight line down. v on top, upside down v on bottom
v
l
l
^
what happens to light rays that hit a concave lens
light rays diverge
light rays diverge when they hit a concave lens. Another way to describe what concave lenses do to light rays is to say that concave lenses make
concave lenses make light rays spread out
if the lines leaving the concave lens are plotted back behind the lens, what do we find
the lines come to a point
the point where the rays meet in a ray diagrams is called….
the principle focus
do concave lenses focus the light rays at the principle focus. explain your answer
no, the light rays only appear to be coming from principle focus
describe ray for concave lens
-draw diagonal ray from top of object through centre of lens, without changing direction
-another ray from top of object
passes through lens and then refracted out
-draw dotted line so this ray appears to come from principle focus
-where dotted line and first line drawn meets show image position
describe 3 properties of image made in ray diagram for concave lens
image diminished
image right way up
image is virtual
why is the image made in a ray diagram for concave lenses considered virtual
because rays do not actually cross
if we place a screen where the image appears, we would not see an image
with a concave lens the image will always be…….
1
2
3
diminished
right way up
virtual
(any order)
during reflection the angle of reflection is…….
the same as the angle of incidence
define specular reflection
reflection from a smooth surface in a single direction
what does specular reflection do
produce an image
define diffuse reflection
reflection from a rough surface causes scattering
does diffuse reflection produce an image
no
what is white light
a mixture of all the different colours
what happens to white light when passed through a prism
it splits into a spectrum
what 2 things does each colour in the visible light spectrum have
own narrow band of wavelength
own narrow band of frequency
what does the colour of an object depend on
which wavelengths of light are reflected, transmitted or absorbed
how do colour filters work
by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour)
what is meant by saying a colour filter transmitts a wavelength
allows the wavelength through
what happens when you shine white light onto a red filter
(this is applicable to any colour from the visible light spectrum)
-filter absorbs all colours of visible light except from red
-only red light is transmitted through the filter
objects that transmit light can be 1 of two things. What are these
transparent
translucent
what do translucent objects do
what is the effect of this
scatter light rays.
can’t see through them clearly
what do we call objects that we cannot see through at all
opaque
why do white objects appear white
they reflect all of the wavelengths of visible light equally
why do black objects appear black
they absorb all the wavelengths of visible light
how is the colour of an opaque object determined
by which wavelengths of light (which colours) are more strongly reflected and which are absorbed
white light shines onto a blue object, why does object have blue colour
all the colours are absorbed- except from blue- which is reflected
there is a red object on table
and red filter above object
white light shines onto filter
what happens
red filter absorbs all the colours of white light, apart from red
red is transmitted
red light reflects off red object
so object appears red
there is a green object on a table
and red filter above it
white light shines onto filter
what happens
red filter absorbs all colours of white light except red
red is transmitted
green object absorbs all the red light thats transmitted instead of reflecting it
green object appears black as its not reflecting any light
when does an opaque object appear black
when it does not reflect any light
what surfaces are the best emitters and absorbers of infrared radiation
matt black
true or false+ why
objects below 5 degrees do not emit infrared radiation
objects above 600 degrees do not absorb infrared radiation
FALSE
All objects emit AND absorb infrared REGARDLESS of temperature
in a given time, which object will emit more infrared, a cooler object or a hotter one
a hotter object
what do the wavelength and intensity of radiation depend on
the temp of the object
how does the size of the wavelength of the radiation depend on the temp of the object
as the object gets hotter, it emits more short wavelength radiation
…… hot objects emit ….. wavelength ….. than ….. objects
very hot objects emit shorter wavelength radiation then cooler objects
how are the intensity of radiation and wavelength related
shorter wavelength means higher intensity of radiation
why do very hot objects produce visible light
because as an object gets hotter, it emits more short wavelength radiation
what happens to the intensity of radiation at higher temperature
intensity increases at higher temps
define a perfect black body
an object that absorbs all the radiation incident on it
a black body does not ….. or ….. any radiation
A black body does not reflect or transmit any
radiation.
an object than ……. radiation well will also …… radiation well
absorbs
emits
a perfect black body is an object that absorbs all the radiation incident on it. Since a good absorber of radiation is also a good emitter of radiation, a perfect black body would be
the best possible emitter
what will an object do if warmer than surroundings
emit more radiation than it absorbs
if an object emits more radiation than it absorbs, what will happen to the object
it temp will decrease
what will an object do if cooler than its surroundings
absorb more radiation than it emits
if an object absorbs more radiation than it emits, what will happen to the object
its temp increase
what will an object do if its at a constant temp
absorb and emit radiation at the same rate
what are the only two ways earth can lose / gain energy
emitting radiation
absorbing radiation
what does the sun do to radiation
what type of radiation
example of that type of radiation
emits radiation
short wavelength radiation
eg visible light
what can happen to the radiation emitted by sun
what does this cause
reflected by clouds
absorbed by earths surface
causes temp of earth to increase
what happens to infrared radiation on earth
emitted back into space
some gets trapped by greenhouse gases
human activity is increasing the levels of
green house gases in the atmosphere
what is the effect of increased greenhouse gases
more heat energy trapped in atmosphere
less radiated into space
what factors other than greenhouse gases affect amount of energy radiated from earth
amount of cloud cover
why are cloudy nights warmer than clear night
clouds reflect infrared back to earth
( prevent infrared from being radiated to space)
