P1e: Cooking and communicating using waves Flashcards
Describe properties of infrared radiation(2)
heats the surface of the food as it does not penetrate food easily
is reflected by shiny surfaces
Describe properties of microwaves(4)
penetrate (~1cm) into food
are reflected by shiny metal surfaces
can cause burns when absorbed by body tissue
pass through glass and plastics
How does IR transfer energy to materials? (2)
IR is absorbed only by particles on the surface of the food, increasing their KE
KE is transferred to the center of the food by conduction or convection
How do microwaves transfer energy to materials? (2)
microwaves are absorbed only by water or fat particles in outer layers of the food, increasing their KE
KE is transferred to the rest of the food by conduction or convection
Why does signal loss with microwaves happen? (5)
hills and buildings get in the way too much, signals cannot get through
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 unlike radio waves, making line of sigh more important
interference between other EM wave signals
How are the problems of signal loss with microwaves reduced? (2)
limiting the distance between transmitters to ensure the signal received remains strong
high positioning of transmitters on hills to avoid other obstructions
Who is at “risk” because of microwave communications?(2)
residents near the site of a mobile phone transmitter mast
users of mobile phones
Why may there be dangers to microwave communication?
some research has shown that microwaves can penetrate skin and cause a small heating effect in the brain
Why may there not be dangers to microwave communication?(2)
Different studies have produced different results and reached conflicting conclusions about the potential dangers of mobile phone
use
lack of clear evidence of any increased risk either way
In the presence of conflicting evidence, what must individuals and society do?
people must make choices about mobile phone usage and about location of masts in terms of balancing potential risks and known benefits
How can potential dangers be increased
by frequent use
What does publishing scientific studies into the
effects of mobile phone microwave radiation allow
allows the results to be checked
What does there need to be for microwave communication?
line of sight between the transmitter (phone) and the receiver (phone mast)
