SCIENCE: Uses and Effects of Electromagnetic Waves

communication technologies

Uses of Radio Waves

communication in submarines

communication inside mines

communication inside caves

lightning

Uses of ELF radio waves

lightning

Uses of VLF radio waves

Marine radio

Aviation radio

Commercial AM (amplitude modulation) radio

Uses of LF radio waves & MF radio waves

Interference —> Sound quality

Uses of AM radio waves

FM Radio

Broadcast television sound

Public service radio

Cellphones

GPS (Global positioning system)

Frequency Modulation (FM)

Uses of HF, VHF, & UHF Radio Waves

Shortwave stations thousands of miles

Uses of Shortwave Radio

Wi-Fi

Bluetooth

Wireless USB (Universal Serial Bus)

Radar

Uses of SHF & EHF Radio Waves

Substances hot

Mobile phones

Wifi

Fixed traffic speed cameras

Radar

Uses of Microwave

"Cataracts"

"Cooked"

Effects of Microwave

Stars

Lamps

Flames

Remote controls

Heat lamps - heal sports injuries (physiotherapists)

Mobile phones

Dolby Screentalk Headset system

Night sights - Sensitive IR detector

“Passive Infra-Red" (PIR) Detectors

Police helicopters - Thermal imaging

Weather forecasters - IR cameras

Uses of Infrared

Lasers in Compact Disc and DVD players

Laser printers

Laser in Aircraft weapon aiming systems

Uses of Visible light

Damage retina

Effects of Visible light

Sun tan

Forged bank notes detector

Hardening of dental filling

UV lamps or backlights

Kill microbes

Sterilize

Vitamin D

Uses of Ultraviolet

Damage retina

Sunburn

Skin cancer

Effects of Ultraviolet

Airport security

Astronomers - suitable radio telescopes

Scan soft areas

Uses of X-rays

Cell damage

Cancers

Effects of X-rays

Kill cancer cells

Radiotherapy

Sterilize food

Sterilize medical equipment

Uses of Gamma Rays

Cell damage

Cancers

Mutations

Effects of Gamma Rays

0.04 inches (1 millimeter) to more than 62 miles (100 kilometers)

range of longest wavelengths

3,000 cycles per second or 3 kilohertz, up to about 300 billion hertz or 300 gigahertz

range of lowest frequencies

Heinrich Hertz

the first person to transmit and receive controlled radio waves

hertz (Hz)

unit of frequency of an EM wave - one cycle per second

Sound waves, microphone, electrical impulses

electrical impulses, radio waves, transmitter

radio waves, radio receiver, sound

How do radio waves work?

— enter the — and are converted into —-.

The — are converted into — and broadcast by the —-.

The — reach a — and are converted back into —.

ELF radio waves

have a long range and are useful in penetrating water and rock for communication with submarines and inside mines and caves

lightning

most powerful natural source of ELF/VLF waves

lightning strikes

waves produced by — can bounce back and forth between earth and the ionosphere

AM radio wave

has a long range, particularly at night when the ionosphere is better at refracting tne waves back to earth

AM radio wave

subject to interference that affects sound quality

frequency modulation (FM)

what does HF, VHF, and UHF typically use to encode an audio or data signal onto the carrier wave

frequency modulation, amplitude, frequency, magnitude, audio, data signal

In —, the — of the signal remains constant while the — is varied higher or lower at a rate and — corresponding to the — or —

FM, AM

— results in better signal quality than — because environmental factors do not affect the frequency the way they affect amplitude, and the receiver ignores variations in amplitude as long as the signal remains above a minimum threshold.

HF band, 1.7 megahertz to 30 megahertz

shortwave radio uses frequencies in what band? from about?

ionosphere

Shortwave stations can be heard for thousands of miles because the signals bounce off the —, and rebound back hundreds from their point of origin.

SHF and EHF

highest frequencies in the radio band

microwave band

SHF and EHF are sometimes considered to be part of?

radio wave

less affected by air so it has short-range applications

water and fat molecules

microwaves causes what molecules to vibrate?

antenna

in microwaves, mobile phones should have what in order to be generated which means that the phone doesn’t need to be very big?

cataracts

prolonged exposure to significant levels of microwaves is known to cause “—-” in your eyes, which is a clouding of the lens preventing you from seeing clearly.

microwaves, cooked

people who work on aircraft carrier decks wear special suits which reflect —-, to avoid being “—-” by the powerful radar units in modern military planes

infra red waves

just below visible red light in the electromagnetic spectrum

infrared

given off by hot objects, and you can feel them as warmth on your skin

stars

lamps

flames

infrared are also given off by?

Passive Infra-Red (PIR) detectors

used in burglar alarm systems, and to control the security lightning

Passive Infra-Red (PIR) detectors

these detect the infra-red emitted by people and animals

thermal imaging

we can see in the dark

visible light

our eyes can detect only a tiny part of the electromagnetic spectrum, called?

white light

made of a whole range of colors, mixed together

retina

too much light can damage —- in your eye

sun

in visible light, you should avoid looking at something very bright such as the —-

fluoresce

in clubs, where they make your clothes glow, this happens because substances in washing powder “—-” when UV light strikes them - they absorb the UV and then re-radiate the energy at a longer wavelength

retina

ultraviolet can also damage the — in your eye that’s why it’s important to check that your sunglasses will block UV light

x-ray

very high frequency waves, and carry a lot of energy

x-rays

they will pass through most substances, and this makes them useful in medicine and industry to see inside things

x-rays

used by doctors to see inside people

x-rays

do not pass through tissues easily

radiographers

— in hospitals stand behind a shield when they x-ray their patients

gamma rays

given off by stars and by some radioactive substances

gamma rays

extremely high frequency waves and carry large amount of energy

gamma-rays

pass through most materials, and are quite difficult to stop - you need lead or concrete in order to block them out

irradiated food

what food does gamma rays sterilize?

study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation

spectroscopy