Electromagnetic Waves &the Electromagnetic Spectrum

The Electromagnetic Spectrum• The name given to a group of energy waves that are mostly

invisible and can travel through empty space

• Longer waves have less energy

• Shorter waves have more energy and longer waves have less energy

longest wavelength shortest wavelength

Waves… a review

Most waves are either longitudinal or transverse.

Sound waves are longitudinal.But all electromagnetic waves are

transverse…

Electromagnetic waves

Produced by the movement of electrically charged particles

Can travel in a “vacuum” (they do NOT need a medium)

Travel at the speed of light 300,000 km/s

Also known as EM waves

Electromagnetic Waves• Transverse waves without a medium!• (They can travel through empty space)

Electromagnetic waves travel VERY FAST – around 300,000

kilometres per second (the speed of light).

At this speed they can go around the world 8 times in one second.

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency

RADIO WAVES

MICROWAVES

INFRARED RAYS

VISIBLE LIGHT

ULTRAVIOLET RAYS

X-RAYS

GAMMA RAYS

Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

RADIO WAVESHave the longestwavelengths and

lowestfrequencies of

all the electromagnetic

waves.

Types of EM Radiation

Radiowaves– lowest energy EM radiation

Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from

several satellites to the receiver, determining the distance to each satellite.

Radio waves

Longest wavelength EM wavesUses:

– TV broadcasting– AM and FM broadcast radio– Heart rate monitors– Cell phone communication– MRI (MAGNETIC RESONACE IMAGING)

• Uses Short wave radio waves with a magnet to create an image

Radio waves

Longest wavelength EM wavesUses:

– TV broadcasting– AM and FM broadcast radio– Heart rate monitors– Cell phone communication– MRI (MAGNETIC RESONACE IMAGING)

• Uses Short wave radio waves with a magnet to create an image

MICROWAVES

Have the shortest

wavelengths and the highest

frequency of the radio waves.

Microwaves

Wavelengths from 1 mm- 1 mUses:

– Microwave ovens– Bluetooth headsets– Broadband Wireless Internet– Radar– GPS

RADAR (Radio Detection and Ranging)• Used to find the

speed of an object by sending out radio waves and measuring the time it takes them to return.

INFRARED RAYS

Infrared= below red

Shorter wavelength and

higher frequency than

microwaves.

Infrared Radiation

Wavelengths in between microwaves and visible light

Uses:– Night vision goggles– Remote controls– Heat-seeking missiles

VISIBLE LIGHTShorter wavelength and

higher frequency than infrared rays.

Electromagnetic waves we can see.

Longest wavelength= red light

Shortest wavelength= violet (purple) light

Visible lightOnly type of EM wave able to be

detected by the human eyeViolet is the highest frequency

lightRed light is the lowest frequency

light

When light enters a new medium it

bends (refracts). Each wavelength

bends a different amount allowing white light to

separate into it’s various colors ROYGBIV.

ULTRAVIOLET RAYSShorter

wavelength and higher

frequency than visible lightCarry more energy than visible light

UltravioletShorter wavelengths than visible lightUses:

– Black lights– Security images on money– Harmful to living things

• Used to sterilize medical equipment• Too much causes sun burn• Extremely high exposure can cause skin cancer

X- RAYSShorter

wavelength and higher

frequency than UV-rays

Carry a great amount of

energyCan penetrate

most matter.

X-rays

Tiny wavelength, high energy waves

Uses:– Medical imaging– Airport security

• Moderate dose can damaging to cells

Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-

ray was absorbed)

Used by engineersto check for tiny cracks in structures.– The rays pass

through the cracks and the cracks appear dark on film.

GAMMA RAYS

Shorter wavelength and higher frequency

than X-raysCarry the greatest amount of energyand penetrate the

most.

Gamma RaysSmallest wavelengths, highest energy EM

wavesUsesSterilizes medical equipmentCancer treatment to kill cancer cellsKills nearly all living cells.

Used in radiation treatment to kill cancer cells.

Can be very harmful if not used correctly.

Exploding nuclear

weapons emit gamma rays.

Brief SUMMARYA. All electromagnetic waves travel at the same

speed. (300,000,000 meters/second) in a vacuum.

B. They all have different wavelengths and different frequencies.– Long wavelength-lowest frequency– Short wavelength highest frequency– The higher the frequency the higher the energy.