P13 Electromagnetic spectrum (paper 2) Flashcards
What are electromagnetic waves
transverse waves that transfer energy from a source to an absorber
what speed do EM waves travel through air or a vacuum
the same speed - the speed of light
what spectrum do electromagnetic waves form
a continuous spectrum over a range of frequencies
how can EM waves be grouped and ranked
in terms of frequency and wavelength into seven basic types
why is there such a wide range of frequencies for EM waves
because they are generated by a variety of hcnages in atoms and thier nuclei
what are EM waves caused by
something with an electrical charge osillating
what are the seven EM wave types
- radio waves
- microwaves
- infrared waves
- visiable light
- ultraviolet
- x-rays
- gamma rays
which EM wave has the smallest wavelength
gamma rays
which EM wave has the biggest frequency
gamma rays
which EM wave has the biggest wavelength
radio waves
which EM wave has the smallest frequency
radio waves
what are EM waves made up of
oscillating electric and magnetic fields
how can you produce radio waves using an alternating current in an electrical circuit
- the object with the charges (electrons) oscillate to create the radio waves is a transmitter
- when the transmitted radio waves reach a receiver they are absorbed
- the energy carried is transferred to the electrons in the reciever
- causing the electrons to oscillate ~ generating an alternating current
what are radio waves main use
communication
why can long-wave radio waves be recieved even if the receiver isn’t in the line of sight of the transmitter
because long wavelengths diffact (bend) around the curved surface of the Earth, hills or into tunnels
can short-wave radio waves be recieved from long distances and why
yes because they are reflected from the ionosphere
what is the ionosphere
an electrically charged layer in the Earth’s upper atmosphere
what type of radio waves does bluetooth use
short-wave radio waves
what are microwaves used for
satellite communication and microwave ovens
why are microwaves best for satellite communication
because they pass easily through the Earth’s watery atmosphere
how does satellite communication work
- signal from transmitter is transmitted into space
- picked up by satellite receiver dish
- satellite transmits the sign back down to earth
- it is received by a satellite dish on the ground
how do microwaves work in microwave ovens
- the microwaves are absorbed by the water molecules in the food
- transferring the energy to the water molecules causing the food to heat up
what can infrared radiation be used to do
increase or monitor temperatures
describe the relationship between hot objects and infrared radiation
the hotter the object the more infrared radiation it gives out
how do infrared cameras work
- camera detects the IR radiation and turns it into an electrical signal which is displayed on a screen
- the hotter the object the brighter it appears
how do electrical heaters heat a room
- the wire heats up inside the heater
- the wire emits lots of IR radiation
- it is absorbed by the objects and the air in the room
- transferring the energy to the thermal energy stores of the objects
what can visible light be used for
in fibre optic cables to transmit data
what are fibre optic cables
thin glass or plastic fibres that can carry data (from phones or TVs) over long distances as pulses of visible light
how do fibre optics work
the light rays reflect and bounce back and fourth until they reach the end of the fibre
what is fluorescence
a property of certain chemicals where ultraviolet radiation is absorbed and then visible light is emitted
what are the uses of ultraviolet radiation
- tanning
- fluorescent lights
- sterelising
what is UV produced by
the sun
what are x-rays and gamma rays used for
- sterilise
- security in airports
- imaging in medicine
how do x-ray photographs work
- x-rays easily pass through flesh but not rhough denserr metals like bones and metal
- the amount of radiation absorbed gives you an image
what do radiographers use x-rays and gamma rays for
to treat people with cancer using radiotherapy
how does radiotherapy work
- high doses of x-rays and gamma rays kill all living cells
- directing them onto cancer cells can killl them
how do medical professionals stay safe when using x-rays and gamma rays
- wear lead aprons
- stand behind a lead screen
- leave the room
why do medics use lead to protect themselves from rays
because lead is very dense and a good absorber so it will absorb the x-rays and gamma rays
why are ultraviolet, x-rays and gamma rays so dangerous
they are ionising - can knock electrons off of atoms
what does ionising radiation cause
- gene mutation
- cell destruction
- cancer
what is taken into account before ionising EM waves are used
whether the benefits outweigh the health risks
what are radiation doses measured in
sieverts (Sv)
what is radiation dose
a measure of the risk of harm from the body being exposed to radiation
what does the risk of radiation dose depend on
- total amount of radiation
- radiation type
- time exposed
are radiation risks the same amount all over the body
no - it is riskier to have radiation emitted on your chest rather than your head
how do we perceive visible light
as different colours - each colour is it’s own wavelength
when all colours are put together what light does this create
white light
what does the colour and transparency of an objecct depend on
the absorbed wavelengths
why are some objects opaque
because they do not trasmit light - they absorb it and reflect it
what is the colour of an opaque object determined by
which wavelength of light is most reflected
what makes an object white
they reflect all of the visible light wavelengths equally
what makes an object black
they absorb all wavelengths of visible light
what makes an object transparent or translucent
they transmit light - the light is passed through the object not just reflected or absorbed
what are colour filters used for
to filter out different wavelengths of light so only certain wavelengths are transmitted
what is the health probem caused by using sunbeds too much
skin cancer
why are some humans short sighted
because the eyeball is too long
