EM waves and their uses

Question 1

What are the 2 uses of microwaves?

Answer 1

1. Satellite communication 2. Mobile phones

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

They orbit thousands of kilometres above the Earth

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

What kind of satellites use microwaves (excluding communication ones)

Answer 9

REMOTE SENSING satellites

Question 10

What do remote sensing satellites do? (3)

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

What are 2 uses of infrared waves?

Answer 13

1. Wireless remote controls 2. Optical fibres

Question 14

How do remote controls work?

Answer 14

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

Question 15

What can optical fibres do? How quickly?

Answer 15

Optical fibres can carry DATA over LONG DISTANCES Very quickly

Question 16

What 2 EM waves do optical fibres use?

Answer 16

1. Infrared waves
2. Visible light

Question 17

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

Answer 17

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

Question 18

What is visible light commonly used for? (2)

Answer 18

1. Optical fibres
2. Photography

Question 19

What do cameras use to focus visible light?

Answer 19

A lens

Question 20

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

Answer 20

1. A light-sensitive film
2. Electronic sensor

Question 21

What does the lens aperture control?

Answer 21

How much light enters the camera

Question 22

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

Answer 22

The ‘pupil’

Question 23

What does the shutter speed determine?

Answer 23

How long the film or sensor is exposed to the light

Question 24

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

Answer 24

1. Aperture
2. Shutter speed
3. Sensitivity (of the film or the sensor)

Question 25

What is the name of how pulses of light or infrared radiation are reflected through an optical fibre?

Answer 25

Total internal reflection

(NOT ‘refraction’)