Topic 6 - Waves (5)

Question 1

RADIO WAVES:
What are EM waves made up of?

Answer 1

oscillating electric and magnetic fields

Question 2

RADIO WAVES:
What are alternating currents made up of?
How do they produce EM waves?

Answer 2

• alternating currents (ac) are made up of oscillating charges
• as the charges oscillate, they produce oscillating electric and magnetic fields, i.e. electromagnetic waves

Question 3

RADIO WAVES:
What is the frequency of waves produced by ac?

Answer 3

it is equal to the frequency of the alternating current

Question 4

RADIO WAVES:
What are radio waves?

Answer 4

EM radiation with wavelengths longer than about 10cm

Question 5

RADIO WAVES:
What are the wavelengths of long wave radio?

Answer 5

1-10km

Question 6

RADIO WAVES:
Why can long-wave radio signals be transmitted and received halfway around the world?

Answer 6

long wavelengths diffract (bend) around the curved surface of the earth (thay can also diffract around hills and into tunnels)

Question 7

RADIO WAVES:
Why does the ability of long wave signals to diffracts make radio signals useful?

Answer 7

radio signals can be received even if the receiver isn’t in the line of sight of the transmitter

Question 8

RADIO WAVES:
What is the wavelength of short wave radio signals?

Answer 8

10m - 100m

Question 9

RADIO WAVES:
Why can short-wave radio signals be received at long distances from the transmitter?

Answer 9

• they are reflected from the ionosphere - an electrically charged layer in earth’s upper atmosphere

Question 10

RADIO WAVES:
What is the ionosphere?

Answer 10

an electrically charged layer in earth’s upper atmosphere

Question 11

RADIO WAVES:
Give an example of a use of radio waves?

Answer 11

• bluetooth
• TV and FM radio

Question 12

RADIO WAVES:
How doe bluetooth work?

Answer 12

bluetooth uses short-wave radio waves to send data over short distances between devices without wires

Question 13

RADIO WAVES:
Give an example use of bluetooth?

Answer 13

wireless headsets so you can use yout phone while driving a car

Question 14

RADIO WAVES:
Why can (shorter) medium-wave signals only sometimes reflect from the ionosphere?

Answer 14

it depends on the atmospheric conditions and time of day

Question 15

RADIO WAVES:
What radio waves are used for TV and FM radio transmissions?

Answer 15

ones with very short wavelengths

Question 16

RADIO WAVES:
Why do you have to be in direct sight of the transmitter to get reception from TV and FM radio transmissions?

Answer 16

The signal doesn’t bend or travel far through buildings

Question 17

USES OF EM WAVES:
Give a use of visible light?

Answer 17

fibre optic cables

Question 18

USES OF EM WAVES:
What do fibre optic cables do?

Answer 18

use visible light to transmit data

Question 19

USES OF EM WAVES:
What are optical fibres (fibre optic cables)?
What do they do?
What type of EM wave do they use?

Answer 19

they are thin glass or plastic fibres that can carry data (e.g. from telephones or computers) over long distances as pulses of visible light

Question 20

USES OF EM WAVES:
How do optical fibres (fibre optic cables) work?

Answer 20

• they work because of reflection
• light rays are bounced back and forth until they reach the end of the fibre

Question 21

USES OF EM WAVES:
What type of EM wave is used in optcal fibres?

Answer 21

visible light

Question 22

USES OF EM WAVES:
Why is visble light used in fibre optic cables?

Answer 22

light is not easily absorbed or scattered as it travels along a fibre

Question 23

USES OF EM WAVES:
Fluorescence is a property of certain chemicals, what is it?

Answer 23

where ultra-violet radiation (UV) is absorbed and then visible light is emitted (fluorescent colours look so bright because they actually emit light)

Question 24

USES OF EM WAVES:
How do fluorescent lights work?

Answer 24

they generate UV radiation, which is absorbed and re-emitted as visible light by a layer of a compound called a phosphor on the inside of the bulb

Question 25

USES OF EM WAVES: What is an advantage of fluorescent lights?

Answer 25

they are energy-efficient, so they're good when light is needed for long periods (like in the classroom)

Question 26

USES OF EM WAVES: What can security pens be used for? How do they work?

Answer 26

- can be used to mark property with yout name - under UV light the ink will glow (fluorescence), but it's invisible otherwise - this can help the police identify your propety if its stolen

Question 27

USES OF EM WAVES: Exposure to which EM wave gives you a suntan? What is it produced by?

Answer 27

ultra-violet radiation - the sun

Question 28

USES OF EM WAVES: What type of lamp can be used to give an artificial suntan?

Answer 28

UV lamps

Question 29

USES OF EM WAVES: Whya re prople concerned about UV from UV lamps but not fluorescent lights?

Answer 29

fluorescent light emit very little UV - they're totally safe

Question 30

USES OF EM WAVES: How do x-rays in medicine work?

Answer 30

- x-rays pass easily through flesh but not so easily through denser materials like bones or metal - its the amount of radiation that's absorbed or not absorbed that gives you an x-ray image (the brighter bits are where fewer x-rays get through this is a negative image - The plate starts off all white)

Question 31

USES OF EM WAVES: What is the name of the people that use x-rays and gamma rays in medicine?

Answer 31

radiographers

Question 32

USES OF EM WAVES: What is the name of the treatment where x-rays and gamma rays are used to treat people with cancer?

Answer 32

radiotherapy

Question 33

USES OF EM WAVES: What happens in radiotherapy?

Answer 33

- x-rays and gamma rays are used to treat people with cancer - high doses of these rays kill all living cells - they are carefully directed towards cancer cells, to avoid killing too many normal, healthy cells

Question 34

USES OF EM WAVES: State another use of gamma radiation in medicine?

Answer 34

in a medical tracer

Question 35

USES OF EM WAVES: Explain how gamma rays can be used in medical tracers? Why is gamma radiation suited to this use?

Answer 35

- a gamma-emmiting source is injected into the patient, and its progress is followed around the body - gamma radiation is suited to this because it can pass out through the body to be detected

Question 36

USES OF EM WAVES: State three ways radiographers keep their exposure to x-rays and gamma rays to a minimum?

Answer 36

- wear lead aprons - stand behind a lead screen or leave the room

Question 37

DANGERS OF EM WAVES: What are the effects of each type of radiation based on?

Answer 37

how much energy the wave transfers

Question 38

DANGERS OF EM WAVES: Give an example of a low frequency wave? Are they harmful? Why /why not?

Answer 38

- radio waves - often harmless - don't transfer much energy and mostly pass through soft tissue without being absorbed

Question 39

DANGERS OF EM WAVES: Give an example of a high frequency wave? Are they harmful? Why /why not?

Answer 39

- UV, x-rays, gamma rays - can cause lots of damage - all transfer lots of energy

Question 40

DANGERS OF EM WAVES: What are the effects of UV radiation?

Answer 40

- uv radiation damages surface cells, causing - sunburn - skin to age prematurely - blindness - increased risk of skin cancer

Question 41

DANGERS OF EM WAVES: What are x-ray and gamma rays examples of? What does this mean? What can this cause?

Answer 41

ionising radiation - this means they carry enough energy to knock electrons off of atoms - this can cause a gene mutation and cell destruction, and cancer