P1e: Cooking and communicating using waves Flashcards

1
Q

Describe properties of infrared radiation(2)

A

heats the surface of the food as it does not penetrate food easily

is reflected by shiny surfaces

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2
Q

Describe properties of microwaves(4)

A

penetrate (~1cm) into food

are reflected by shiny metal surfaces

can cause burns when absorbed by body tissue

pass through glass and plastics

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3
Q

How does IR transfer energy to materials? (2)

A

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

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4
Q

How do microwaves transfer energy to materials? (2)

A

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

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5
Q

Why does signal loss with microwaves happen? (5)

A

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

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6
Q

How are the problems of signal loss with microwaves reduced? (2)

A

limiting the distance between transmitters to ensure the signal received remains strong

high positioning of transmitters on hills to avoid other obstructions

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7
Q

Who is at “risk” because of microwave communications?(2)

A

residents near the site of a mobile phone transmitter mast

users of mobile phones

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8
Q

Why may there be dangers to microwave communication?

A

some research has shown that microwaves can penetrate skin and cause a small heating effect in the brain

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9
Q

Why may there not be dangers to microwave communication?(2)

A

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

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10
Q

In the presence of conflicting evidence, what must individuals and society do?

A

people must make choices about mobile phone usage and about location of masts in terms of balancing potential risks and known benefits

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11
Q

How can potential dangers be increased

A

by frequent use

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12
Q

What does publishing scientific studies into the

effects of mobile phone microwave radiation allow

A

allows the results to be checked

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13
Q

What does there need to be for microwave communication?

A

line of sight between the transmitter (phone) and the receiver (phone mast)

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