P1e-cooking And Communicating Using Waves Flashcards
How are matt black surfaces affected by heat radiation?
Very good absorbers and emitters of radiation
How are light coloured smooth and shiny objects affected by heat radiation?
Very poor absorbers and emitters of radiation
What are the properties of infrared radiation?
Heats surface of food
Reflected by shiny surfaces
What are the properties of microwaves?
- Penetrate about 1cm into food
- are reflected by shiny metal surfaces
- can cause burns when absorbed by body tissue
- pass through glass and plastics
How is food heated by infrared radiation?
- infrared absorbed by particles on surface of food increasing KE
- KE is transferred to centre of food by conduction or convection
How is food heated by microwaves?
- microwaves absorbed by only water and fat particles in outer layers of food increasing KE
- energy is conducted or convected to other parts
What kind of signals do mobile phones use?
Microwave signals
Why does signal loss with microwaves happen?
- adverse weather and large areas of surface water scatter signals
- loss of line of sight due to curvature of the earth
- no diffraction of microwaves around large objects
- interference between signals
How can signal loss be reduced?
Limiting distance between transmitters
High positioning of transmitters
How are cooler objects affected by heat radiation?
Absorb heat radiation
Temperature increases
What are the assumed dangers with using mobiles and living near phone masts?
- microwaves emitted into body could damage health
- microwaves can kill cells if absorbed
Why is it a choice to use mobiles and live near masts?
No conclusive proof
Conflicting evidence
