Light Electromagnetic and Visible Spectrum. Electromagnetic Waves Consist of changing magnetic and electric fields moving through space at the speed of.

Light Light Electromagnetic Electromagnetic

and Visible and Visible SpectrumSpectrum

Electromagnetic WavesElectromagnetic Waves

Consist of changing magnetic and Consist of changing magnetic and electric fields moving through space electric fields moving through space at the speed of light (3.0 x 10at the speed of light (3.0 x 1088 m/s) m/s)

Are produced by vibrating charged Are produced by vibrating charged particlesparticles

Do not require a mediumDo not require a medium

Electromagnetic SpectrumElectromagnetic Spectrum

Range of frequencies of electromagnetic Range of frequencies of electromagnetic waveswaves

As frequency increases, wavelength As frequency increases, wavelength decreasesdecreases

As frequency increases, energy of a wave As frequency increases, energy of a wave increasesincreases

Electromagnetic Electromagnetic SpectrumSpectrum

The light we can see is The light we can see is only a small part of all only a small part of all light. light.

The whole range is called The whole range is called the electromagnetic the electromagnetic spectrum and visible light spectrum and visible light is in the middle of it.is in the middle of it.

On the low energy end of On the low energy end of the spectrum are radio the spectrum are radio waves. On the high waves. On the high energy end are gamma energy end are gamma rays.rays.

E-M SpectrumE-M Spectrum

Radio waves

Microwaves

Infrared Ultraviolet

Visible

X-rays

Gamma-rays

Radio WavesRadio Waves have the lowest have the lowest frequencyfrequency and the longest and the longest

wavelengthwavelength.. includes includes TVTV waves, which are waves, which are ““vhfvhf”” (very high (very high

frequency) or frequency) or ““uhfuhf”” (ultra high frequency), and (ultra high frequency), and radarradar waves, with highest frequency waves, with highest frequency

Each radio station broadcasts at a set frequency. Each radio station broadcasts at a set frequency. Sound waves are converted into electrical signals Sound waves are converted into electrical signals

and change (modulate) the carrier waves.and change (modulate) the carrier waves.am - am - amplitudeamplitude modulation modulationfm - fm - frequencyfrequency modulation modulation

In receiver antennae, electrons are made to In receiver antennae, electrons are made to vibrate sympathetically at set frequency (concept vibrate sympathetically at set frequency (concept of of resonanceresonance))

MicrowavesMicrowaves

Penetrate food Penetrate food evenlyevenly.. Match the natural frequencies of large Match the natural frequencies of large

molecules, which vibrate and produce molecules, which vibrate and produce heatheat to to cook food from inside.cook food from inside.

AirAir molecules in the oven are too small to be molecules in the oven are too small to be excited, and microwaves also have no effect on excited, and microwaves also have no effect on ceramicsceramics, , plasticplastic, or , or glassglass..

Metals Metals reflectreflect microwaves. microwaves. Droplets of Droplets of waterwater absorb microwaves and form absorb microwaves and form

steam.steam. When food is removed from an oven, molecules When food is removed from an oven, molecules

continue to continue to vibratevibrate, so , so ““standstand”” time is included in time is included in recipes.recipes.

InfraredInfrared

Atoms and moleculesAtoms and molecules vibrate to vibrate to produce infrared waves.produce infrared waves.

All objects emit infrared waves in the All objects emit infrared waves in the form of form of heatheat..

uses for infrared waves:uses for infrared waves:

Sun, fire, radiation, heat lamps used Sun, fire, radiation, heat lamps used in restaurantsin restaurants

Visible LightVisible Light

electromagnetic radiation to which electromagnetic radiation to which human eyeshuman eyes are sensitive. are sensitive.

makes up less than makes up less than 1010-6-6 % of % of electromagnetic spectrumelectromagnetic spectrum

different frequencies are seen as different frequencies are seen as colorscolors..

red – lowest red – lowest frequencyfrequency and and lowestlowest energy energy

violet – highest violet – highest frequencyfrequency and and highesthighest energyenergy

UltravioletUltraviolet

Overexposure can cause Overexposure can cause sunburnssunburns and and skin cancerskin cancer

uses: uses: medicine to sterilize surgical instruments by medicine to sterilize surgical instruments by killing bacteriakilling bacteria

higher UV frequencies are blocked by higher UV frequencies are blocked by gasgas in in atmosphereatmosphere

Fact or Fiction: Sunlight through a window can Fact or Fiction: Sunlight through a window can give you a sunburn? give you a sunburn?

Fiction- Ultraviolet rays can not penetrate through Fiction- Ultraviolet rays can not penetrate through a window. It is infrared waves that are passing a window. It is infrared waves that are passing through and that is why it is warm.through and that is why it is warm.

X-raysX-rays

discovered by discovered by Wilhelm RoentgenWilhelm Roentgen

produced by greatest acceleration of produced by greatest acceleration of electronselectrons..

uses: uses: x-ray machine for bodies or x-ray machine for bodies or teeth, to check luggage at airportsteeth, to check luggage at airports

Gamma RaysGamma Rays

highest highest energyenergy and greatest and greatest penetratingpenetrating powerpower

produced by produced by nuclearnuclear reactions, including reactions, including decay of radioactive atoms and nuclear decay of radioactive atoms and nuclear explosionsexplosions

kills kills cancercancer cells before it kills cells before it kills healthyhealthy cells cells

uses: uses: removing decay-causing bacteria from removing decay-causing bacteria from many foodstuffs or preventing fruit and many foodstuffs or preventing fruit and vegetables from sprouting to maintain vegetables from sprouting to maintain freshness and flavorfreshness and flavor