P13 Electromagnetic spectrum (paper 2)

Question 1

What are electromagnetic waves

Answer 1

transverse waves that transfer energy from a source to an absorber

Question 2

what speed do EM waves travel through air or a vacuum

Answer 2

the same speed - the speed of light

Question 3

what spectrum do electromagnetic waves form

Answer 3

a continuous spectrum over a range of frequencies

Question 4

how can EM waves be grouped and ranked

Answer 4

in terms of frequency and wavelength into seven basic types

Question 5

why is there such a wide range of frequencies for EM waves

Answer 5

because they are generated by a variety of hcnages in atoms and thier nuclei

Question 6

what are EM waves caused by

Answer 6

something with an electrical charge osillating

Question 7

what are the seven EM wave types

Answer 7

• radio waves
• microwaves
• infrared waves
• visiable light
• ultraviolet
• x-rays
• gamma rays

Question 8

which EM wave has the smallest wavelength

Answer 8

gamma rays

Question 9

which EM wave has the biggest frequency

Answer 9

gamma rays

Question 10

which EM wave has the biggest wavelength

Answer 10

radio waves

Question 11

which EM wave has the smallest frequency

Answer 11

radio waves

Question 12

what are EM waves made up of

Answer 12

oscillating electric and magnetic fields

Question 13

how can you produce radio waves using an alternating current in an electrical circuit

Answer 13

• 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

Question 14

what are radio waves main use

Answer 14

communication

Question 15

why can long-wave radio waves be recieved even if the receiver isn’t in the line of sight of the transmitter

Answer 15

because long wavelengths diffact (bend) around the curved surface of the Earth, hills or into tunnels

Question 16

can short-wave radio waves be recieved from long distances and why

Answer 16

yes because they are reflected from the ionosphere

Question 17

what is the ionosphere

Answer 17

an electrically charged layer in the Earth’s upper atmosphere

Question 18

what type of radio waves does bluetooth use

Answer 18

short-wave radio waves

Question 19

what are microwaves used for

Answer 19

satellite communication and microwave ovens

Question 20

why are microwaves best for satellite communication

Answer 20

because they pass easily through the Earth’s watery atmosphere

Question 21

how does satellite communication work

Answer 21

• 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

Question 22

how do microwaves work in microwave ovens

Answer 22

• the microwaves are absorbed by the water molecules in the food
• transferring the energy to the water molecules causing the food to heat up

Question 23

what can infrared radiation be used to do

Answer 23

increase or monitor temperatures

Question 24

describe the relationship between hot objects and infrared radiation

Answer 24

the hotter the object the more infrared radiation it gives out

Question 25

how do infrared cameras work

Answer 25

- 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

Question 26

how do electrical heaters heat a room

Answer 26

- 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

Question 27

what can visible light be used for

Answer 27

in fibre optic cables to transmit data

Question 28

what are fibre optic cables

Answer 28

thin glass or plastic fibres that can carry data (from phones or TVs) over long distances as pulses of visible light

Question 29

how do fibre optics work

Answer 29

the light rays reflect and bounce back and fourth until they reach the end of the fibre

Question 30

what is fluorescence

Answer 30

a property of certain chemicals where ultraviolet radiation is absorbed and then visible light is emitted

Question 31

what are the uses of ultraviolet radiation

Answer 31

- tanning - fluorescent lights - sterelising

Question 32

what is UV produced by

Answer 32

the sun

Question 33

what are x-rays and gamma rays used for

Answer 33

- sterilise - security in airports - imaging in medicine

Question 34

how do x-ray photographs work

Answer 34

- x-rays easily pass through flesh but not rhough denserr metals like bones and metal - the amount of radiation absorbed gives you an image

Question 35

what do radiographers use x-rays and gamma rays for

Answer 35

to treat people with cancer using radiotherapy

Question 36

how does radiotherapy work

Answer 36

- high doses of x-rays and gamma rays kill all living cells - directing them onto cancer cells can killl them

Question 37

how do medical professionals stay safe when using x-rays and gamma rays

Answer 37

- wear lead aprons - stand behind a lead screen - leave the room

Question 38

why do medics use lead to protect themselves from rays

Answer 38

because lead is very dense and a good absorber so it will absorb the x-rays and gamma rays

Question 39

why are ultraviolet, x-rays and gamma rays so dangerous

Answer 39

they are ionising - can knock electrons off of atoms

Question 40

what does ionising radiation cause

Answer 40

- gene mutation - cell destruction - cancer

Question 41

what is taken into account before ionising EM waves are used

Answer 41

whether the benefits outweigh the health risks

Question 42

what are radiation doses measured in

Answer 42

sieverts (Sv)

Question 43

what is radiation dose

Answer 43

a measure of the risk of harm from the body being exposed to radiation

Question 44

what does the risk of radiation dose depend on

Answer 44

- total amount of radiation - radiation type - time exposed

Question 45

are radiation risks the same amount all over the body

Answer 45

no - it is riskier to have radiation emitted on your chest rather than your head

Question 46

how do we perceive visible light

Answer 46

as different colours - each colour is it's own wavelength

Question 47

when all colours are put together what light does this create

Answer 47

white light

Question 48

what does the colour and transparency of an objecct depend on

Answer 48

the absorbed wavelengths

Question 49

why are some objects opaque

Answer 49

because they do not trasmit light - they absorb it and reflect it

Question 50

what is the colour of an opaque object determined by

Answer 50

which wavelength of light is most reflected

Question 51

what makes an object white

Answer 51

they reflect all of the visible light wavelengths equally

Question 52

what makes an object black

Answer 52

they absorb all wavelengths of visible light

Question 53

what makes an object transparent or translucent

Answer 53

they transmit light - the light is passed through the object not just reflected or absorbed

Question 54

what are colour filters used for

Answer 54

to filter out different wavelengths of light so only certain wavelengths are transmitted

Question 55

what is the health probem caused by using sunbeds too much

Answer 55

skin cancer

Question 56

why are some humans short sighted

Answer 56

because the eyeball is too long