P13 - Electromagnetic spectrum Flashcards
electromagnetic waves
electric and magnetic disturbances
- can be used to transfer energy
- from a source to an absorber
-don’t transfer matter
electromagnetic waves - energy transferred depends on
wavelength of waves
Electromagnetic spectrum - starting from longest
radio
microwaves
infrared
visible light
UV radiation
X rays
Gamma radiation
electromagnetic speed
3 hundred million m/s
wave speed formula
frequency x wavelength
human eye can only detect
visible light
-400nm to 700nm
white light produced from
sun
ordinary lamps
white light
all colours of visible spectrum
wavelength of colours
increases from violet to red
hotter an object =
more infrared it emits
infrared absorbed by skin can
burn
kill skin cells as it heats them
Infrared devices eg
-optical fibres in communication systems
optical fibres in communication systems purpose
- will carry signals from remote control handsets + inside optical fibres
microwaves
shorter wavelength than radio
microwaves use
-carry satellite tv programmes + phone calls
-heat food
how do microwaves heat food
-penetrating food
-absorbed by water molecules
-the microwave doesn’t become hot as it hasn’t got water molecules to absorb the heat
radio waves
- used for radio or tv broadcasting
phone calls
mobile phone radiation is
microwaves
near - microwave radio waves
microwaves can heat
internal parts of body
infrared use
heaters
food
cameras
visible light use
fibre optic communications
x rays and gamma eg
medical imaging
treatments
uv use
energy efficient lamps
-tanning beds
carrier waves
waves used to carry any type of signal
carrier waves eg
between phone and nearby phone mast
carrier waves type
can be radio
microwaves
infrared
visible
carrier waves type depends on
how much info in signal
and distance to travel
shorter wavelength carrier waves means=
more info can be carried
-shorter their range
- less they spread out
mobile phones safety?
research is needed to evaluate this
carrier waves will (amplitude)
vary amplitude to carry signals
Radio station process
-microphone produces AC when sound waves reach it
- oscillator supplies carrier waves to transmitter as AC
- modulated carrier waves are supplied to transmitter aerial
- emits radio waves
- absorbed by receiver aerial = induces AC
- causes oscillations in receiver
- receiver circuit separates audio signal from carrier waves
- supplied to loudspeaker which sends out sound waves
AC
audio signal
audio signals to transmitter to
modulate (vary) carrier waves
varying ac to aerial
-causes it to emit radio waves to carry audio signal
frequency of oscillations
frequency of radio waves
optical fibres are
-thin glass fibres
- transmits signal carried by light/infrared
- light cannot escape the fibre
- when they reach the surface = they are reflected back into it
optical fibres use
-carry more info than microwaves/radio
- more secure as signals stay in fibre
why does optical fibres carry more info than radio
light has a shorter wavelength
=more pulses of waves
UV properties
shorter wavelength than visible light
-carries more enrgy
- can harm skin/ eyes (cancer or blindness)
X rays and gamma - penetration
can travel though substances if not too dense
-stopped by thick lead plates
x rays and gamma properties
- short end of wavelength EM spectrum
- carry much more energy per sec
x rays produced when
electrons moving at high speeds are stopped
Gamma rays produced by
radioactive substances when unstable nuclei release energy
- shorter wl than x ray so will penertrate more
x ray uses
medical to make x ray images
gamma use
-kills bacteria in food
- kills bacteria on surgical instruments
- kills cancer cells
x rays and gamma - ionising power
- high
- can cause mutations on living tissue (cancer)
- makes uncharged atoms charged
How x rays work
- x rays from a tube are directed onto patient
- light-proof cassette contains photographic film or a flat panel on other side of patient
what absorbs x rays
-bones
- teeth
- metal objects
how is a radiograph made
- x rays pass through soft tissue
- bone absorbs x ray so it appears lighter
- cavity in tooth appears darker
- soft tissue organs can be filled with a contrats medium to absorb x ray easier
contrast medium for x rays of soft tissue
- barium compound
- good absorber
lead in x rays
prevents x rays from reaching other body parts
flat panel detector
small screen
- charge coupled devices
- CCD
CCD sensors in CCD
convert x rays to light
-light to electric signal
- sent to computer = image
radiation dose
-measure damage done to their body by ionising radiations
radiation dose depends on
-type
- time body has been exposed to
- energy per second absorbed by body
radiation dose is measured in
sievers
Sv
or msv
high radiation dose
kills living cells
low radiation dose
gene mutation = cancer
x ray therapy
destroys cancerous tumours in body
- thick plates stop from reaching other body parts
- the gap where the tumour is
x ray in therapy
- shorter in wavelength
- higher frequency
- more energy
x ray in imaging
- longer wavelength
- lower energy to be absorbed by bones
-not enough to destroy tumours
