P2 Flashcards
what is the electromagnetic spectrum?
the range of radiation on earth
what is the speed of light?
300,000km/s
What is ionisation?
this is where atoms lose an electron and become negatively or positively charged
Which types of radiation cause isonisation?
ultraviolet light
X-rays
Gamma rays
What are the effects of ionising radiation?
- damage human cells
- cause them to die or become cancerous
How do people protect themselves from x-rays?
x-rays cannot be absorbed by dense materials
people stand behind lead or concrete screens
How do microwaves damage cells?
waves heat up water in the cells damaging them
as molecules are good at transferring microwaves into thermal energy
as waves absorbed
cause water in molecules to heat up and may damage the cell
What are microwaves used for?
heating water in food
the walls and doors absorb or reflect the waves in the micro waves
also low intensity micro waves used in phones
no evidence of harm
What can over exposure to ultraviolet light cause?
sunburn, skin cancer
How can sunburn or skin cancer be prevented?
where clothes or use suncream
also these waves are blocked by the ozone layer
so strenghing that will help
How is ultraviolet light absorbed by the ozone layer?
Ozone is O3 and the ultraviolet light breaks down the ozone into oxygen
the radiation is absorbed and the free oxygen molecule
can join up with other oxygen atoms to make ozone again
What has damaged the ozone layer/
CFCs which are released from fridges and deoderent
these covert ozone into oxygen which allows the ultraviolet radiation to pass through the atmosphere
What can some electromegnetic waves be used for?
communication- radio and microwaves
as they cannot be absorbed by air
long distance internet connection-infared and visible light
What is an analogue signal?
-this is a signal that can have any value
varies continuously
like sine wave
What is a digital wave?
this wave can only be a 0 or a 1
0=off 1=on
How is digital information stored?
stored in bytes
bytes= a string of eight binary digits
more binary code the greater the quality of the information
easily stored in electronic memories of computers
What are the advantages of digital transmission?
- information can be processed by microprocessors in phones or computers
- information can be transported faster
- can be stored in electronic memories which take little space
- information does not lose quality
analogue loses quality as it pick up noise
the signal is only amplified to improve quality while digital is processed through a renegerator which removes the noise
