EM waves and their uses Flashcards

1
Q

What are the 2 uses of microwaves?

A
  1. Satellite communication 2. Mobile phones
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2
Q

Why are microwaves used for communication to and from satellites, not radio waves?

A

Microwaves can PASS EASILY through the Earth’s WATERY ATMOSPHERE- Radio waves can’t

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3
Q

Describe the journey of TV signal from a transmitter to a satellite dish. (for satellite TV) (4)

A
  1. The signal from a transmitter is transmitted into space 2. It’s picked up by the satellite’s RECEIVER DISH 3. The satellite TRANSMITS the signal back to Earth in a DIFFERENT direction 4. It’s received by SATELLITE DISH on the ground
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4
Q

Give a bit more detail on the satellites used for receiving and transmitting signals for TV

A

They orbit thousands of kilometres above the Earth

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5
Q

Mobile phone calls travel as _______ between your phone and the nearest _______

A

Mobile phone calls travel as MICROWAVES between your phone and the nearest TRANSMITTER

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6
Q

Some wavelengths of microwaves are _______ by ______ ______ and __ __ __

A

Some wavelengths of microwaves are ABSORBED by WATER MOLECULES and HEAT them up

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7
Q

How can microwaves damage your health, and what has this caused people to think?

A
  1. Microwaves heat up water, so if it heats up the water in your cells you can start to cook 2. So people think: using your mobile a lot or living near a MAST could damage your health
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8
Q

Is there any conclusive evidence to prove that using your mobile a lot or living near a mast could damage your health?

A

No, though there also isn’t any to prove that it doesn’t

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9
Q

What kind of satellites use microwaves (excluding communication ones)

A

REMOTE SENSING satellites

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10
Q

What do remote sensing satellites do? (3)

A
  1. Monitor oil spills 2. Track the movement of icebergs 3. Monitor deforestation etc
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11
Q

What is an argument against microwaves used for mobile phones causing health risks?

A

One study on the effects of mobile phones on looked at over 400,000 people no connection mobile phone use and occurrence and brain tumours

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12
Q

What is an argument FOR microwaves used for mobile phones causing health risks?

A

Mobile phone use has INCREASED DRAMATICALLY in the last 15 years there may be LONG TERM EFFECTS that we DON’T KNOW about

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13
Q

What are 2 uses of infrared waves?

A
  1. Wireless remote controls 2. Optical fibres
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14
Q

How do remote controls work?

A

By emitting different PATTERNS of infrared waves to send different COMMANDS to an appliance

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15
Q

What can optical fibres do? How quickly?

A

Optical fibres can carry DATA over LONG DISTANCES Very quickly

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16
Q

What 2 EM waves do optical fibres use?

A
  1. Infrared waves
  2. Visible light
17
Q

Describe how optical fibres carry their signal. (3 bits)

A
  1. The signal is carried as pulses of light or infrared radiation
  2. It is reflected off the sides of a very narrow core
  3. from one end of the fibre to the other
18
Q

What is visible light commonly used for? (2)

A
  1. Optical fibres
  2. Photography
19
Q

What do cameras use to focus visible light?

20
Q

What does a camera’s lens focus visible light onto? (2)

A
  1. A light-sensitive film
  2. Electronic sensor
21
Q

What does the lens aperture control?

A

How much light enters the camera

22
Q

What is the eye’s equivilant of the ‘lens’?

A

The ‘pupil

23
Q

What does the shutter speed determine?

A

How long the film or sensor is exposed to the light

24
Q

What are the 3 things photographers can vary to capture as much or as little light they want in their photograph?

A
  1. Aperture
  2. Shutter speed
  3. Sensitivity (of the film or the sensor)
25
What is the name of how pulses of light or infrared radiation are reflected through an optical fibre?
Total internal ref**le**ction (NOT 'refraction')