!! 6.6.2, Electromagnetic waves

Question 1

what are electromagnetic waves

Answer 1

transverse waves

transfer energy from the source of the waves to an absorber

Question 2

list the electromagnetic spectrum from long to short wavelength (low to high frequency)

Answer 2

radio waves
microwaves
infared
visible light
ultraviolet
x-rays
gamma rays

Question 3

how many electromagnetic waves can our eyes detect

Answer 3

our eyes only detect visible light

so detect a limited range of electromagnetic waves

Question 4

4 uses of gamma rays

Answer 4

medical imaging and therapy

astronomy

sterilisation

food preservation

(destorying bacteria and tumors)

Question 5

3 uses of x-rays

including @ low and high energy

Answer 5

low-energy used for medical and industrial imaging

high-energy used to treat cancer

also used for security purposes to detect weapons in airports

Question 6

risks of exposure to x-rays

and safety precautions

Answer 6

highly ionising

doctors ect will leave the room or place mateirals (e.g lead) between themselves and the machine

Question 7

how does ultraviolet light work in lamps and tanning beds

Answer 7

lamps= UV photons give energy to atoms

atoms then release invisible light

sun tanning = UV gives energy to skin cells

the skin cells then change colour

Question 8

7 uses of ultraviolet light

Answer 8

tanning beds

lamps

medical and forensic photography

air purification

disinfection

medical therapy

to detect fake bank notes

Question 9

risks of exposure to too much ultraviolet light

Answer 9

skin burns

skin cancer

cataract formations in the eye

Question 10

how many minisieverts (mSv) is 1 sievert (Sv) equal to

Answer 10

1000 mSv

Question 11

2 uses of infared radiation

Answer 11

in TV controls

also for security purposes, such as in intruder alarms by detecting body heat

Question 12

risks of infared

Answer 12

can cause serious skin burns if emmited from high enough intensities

Question 13

3 uses of microwaves

Answer 13

satellite communications (transmitting signals between stations on Earth and satellites)

to transmit signal from a nearby phone mast to a mobile phone

Microwaves are absorbed by water, heating up the water in the process- useful for heating up lots of food

Question 14

what are radio waves used for and why

Answer 14

for radio and TV communications

as radio waves have long wavelengths, they can be transmitted (sent) around the Earth’s surface and around buildings without interference

Question 15

how can electromagnetic waves be produced

Answer 15

by electrical circuits and by changes in atoms

Question 16

how can eletrical currents produce electromagnetic waves

Answer 16

oscillations in electrical circuits can produce radio waves

when radio waves are absorbed, they can create an alternating current with the same frequency as the radio wave itself

meaning that radio waves can lead to oscillations in an electrical circuit

Question 17

how can changes in atoms produce electromagnetic waves

Answer 17

changes in atoms and the nuclei of atoms can result in electromagnetic waves being generated or absorbed over a wide frequency range

gamma rays originate from changes in the nucleus of an atom

Question 18

where do gamma rays come form

Answer 18

the nucleus of an atom

Question 19

why does the frequency of waves never change

Answer 19

because the source is producing the same number of oscillations (vibrations) per second

Question 20

when does the speed and wavelength of a wave change

how are the speed and wavelength of a wave directly proportional

Answer 20

the speed and wavelength of a wave changes when it travels from one medium to another

directly proportional:
If the speed doubles, the wavelength doubles
If the speed halves, the wavelength halves