http://fc69.deviantart.com/fs36/f/2008/263/8/d/Explosion_of_Light_by_Bunniesandsheep.jpg

Daniel Arnold

Giovanni Cassarino

William Hang

Benjamin Hulbert

Jerry Nguyen

Matthew Robison

Jared Sarabia

EM Waves in a Vacuum• EM fields and waves can exist in a complete

vacuum.• EM waves are disturbances that vary in

frequency.• Without matter to disperse their energy, EM

waves travel forever.• They travel at the speed of light (c=186,000 miles/sec in a vacuum).

Electromagnetic Waves

• An EM wave is a disturbance in both a magnetic and an electric field.

• Most are invisible to us.• Some can be felt as

heat.• Light is an EM wave.

http://www.astronomynotes.com/light/emanim.gif

Radiation and Photons

• EM waves travel out from a source.• Energy that moves in the form of EM waves is

called radiation.• EM radiation is produced by particles of

energy called photons.• A photon goes away when it is absorbed by

matter.

Electromagnetic Spectrum• The EM spectrum describes all frequencies of light.• They are measured in Hertz: cycles per second.• The ranges of EM waves include:

– radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays.

http://science.hq.nasa.gov/kids/imagers/ems/waves.html

Radio Waves• Radio waves are the lowest

frequency.• They can be produced by varying

electric current in a wire.• Radio waves can be used to send

signals by varying the strength and/or the frequencies of the waves.

Gamma

X-ray

Microwave

Infrared

Visible

Radio

Ultraviolet

Radio Waves

http://upload.wikimedia.org/wikipedia/commons/7/72/Radio_transmition_diagram_en.png

Microwaves

• Radar bounces microwaves off of objects to determine their distance and speed.

• Microwave ovens use microwaves to heat and cook food.

Gamma

X-ray

Microwave

Infrared

Visible

Radio

Ultraviolet

http://upload.wikimedia.org/wikipedia/commons/4/43/C-band_Radar-dish_Antenna.jpg

• Cell phones use microwaves to send information to base stations.

Infrared Radiation• Infrared waves are of slightly lower frequencies than

visible light.• They are given off by all matter.• Night-vision goggles detect IR reflected by objects,

allowing one to see in the dark.

Gamma

X-ray

Microwave

InfraredVisible

Radio

Ultraviolet

http://www.i-globalmall.com/uploaded_images/Aevex_Glove_2_270x359-718150.jpg

• Visible light occupies the narrowest range of the EM spectrum.

• The lowest frequencies are seen as red, and the highest are seen as violet.

Gamma

X-ray

Microwave

InfraredVisible

Radio

Ultraviolet

Visible Light

http://www.faqs.org/photo-dict/photofiles/list/699/1110prism.jpg

Gamma

X-ray

Microwave

InfraredVisible

Radio

Ultraviolet

• UV light is invisible to humans.• It can break apart molecules.• It can damage cells if exposed to

them for long periods of time.

http://www.embedds.com/wp-content/uploads/2007i/0711/Ultraviolet_box_pcb.jpg

Ultraviolet Light

X-rays• X-rays are very high frequency and

can pass through some matter.• They can cause cancer.Microwave

Infrared

Visible

Radio

Ultraviolet

http://www.spectrumdata.com.au/uploads/Xray_hand.jpg

Gamma Rays• Gamma rays can pass through more

objects than x-rays.• They are produced by nuclear

explosions and radioactive materials.

• They can cause severe damage to cells and are used to fight cancer.

Microwave

Infrared

Visible

Radio

Ultraviolet

http://jcconwell.files.wordpress.com/2009/07/supernova.jpg

Hot Matter Emits Light

• EM radiation is converted to light.• Incandescent matter emits light.• Light is produced by hot matter.• Hotter matter emits more energy,

and therefore light of higher frequencies.

• Light bulbs heat filaments to produce light.

http://rakadd.files.wordpress.com/2009/10/11_12_52-electric-light-bulb_web.jpg

Chemical Reactions Emit Light

• Animals that give off light are bioluminescent.• This light is cool.• It is produced by a chemical reaction.

http://b9hummingbirdhovering.files.wordpress.com/2009/05/firefly-glowwyrm.jpg

Charged Particles and Radiation

• Auroras are energized by fast-moving charged particles.

• When a gas emits light the light is a distinct color depending on the gas.

• Materials can get energy to produce radiation by first absorbing radiation.

http://climatelab.org/@api/deki/files/191/=Compact_Fluorescent_Light_Bulb.jpg

Other Sources of Energy

• Some materials give off light when squeezed or broken.

• Semiconductors produce infrared light when a current is applied.

• The can also produce visible light as an light-emitting diode (LED).

http://upload.wikimedia.org/wikipedia/commons/e/e9/Red_led_x5.jpg

How does light interact with matter?

• Light connects with matter in three basic ways: – transmitted, – reflected, and – absorbed.

Transmitted Light

• Matter can transmit light or let it pass by. Some materials such as air or clear glass for example glass windows allow light to come straight through. It can also be diffuse or spread out in many directions such as clouds or thin paper. http://livingindryden.org/images/home/finishedWindow06052005B.jpg

Reflected Light

• There are some materials, like books, that light can’t pass. So instead it reflects, or it bounces off of them.

http://staffweb.wylieisd.net/staff/penciek/books3.gif

Adsorbed Light

• Light also can be absorbed by matter taking the energy of it. It is absorbed at the surface of a material.

http://www.shortcourses.com/images/b4ch4/greenobject.jpg

Conclusion

• Most objects around us react to light in a different way. When light bounces off an object in the direction you’re in, your eye will detect it and you will see the object.

Color From Light

• Visible light is a mixture of different frequencies of light, which is detected by your eyes and produces light in side your brain.

• Depending on the properties of your eyes determines the color or shade that is produced.

Rod and Cone Cells• Cone and Rod cells in your eye detect the

brightness of light.• Rod cells are long, thin cells that allow your eyes to

see dim light such as moonlight.• Cone cells are cone shaped cells that detect high

levels of light and allow you to see color.

http://www.uphs.upenn.edu/news/News_Releases/jun07/photoreceptor-diagram.jpg

Primary Colors of Light

• Originally light is split up into three colors, Red, Blue, and Green.

• When these colors mix they create the Pinks, Light Blues, Yellows and so on that we normally see.

http://www.nitride.co.jp/english/images/tpcs.gif

Summary

• Light is an electromagnetic wave.– EM spectrum is divided by frequencies into 7

types.

• Light is produced in different ways.– Chemical, charged particles, radiation, etc.

• Light interacts with materials.– Absorption, transmission, reflection.

• Color comes from light.– Combinations of red, green, and blue.