RIGHT PAGE October 18, 2012

Focus: Light and Sight

Objective: I will be able to explain the relationship among visible light, the electromagnetic spectrum, and sight.

EQ: How does our eyes process light?

HW: project

Warm-Up: Wave Review

(directions are on the sheet)

A light review:• Our primary source of light is the sun.• Light travels in straight lines at a speed of

186,000miles per second.• Light waves travel faster than sound waves.• Light energy from the sun travels through space ,

reaches earth, and some of it turns to heat energy and warms the earth’s air.

• Light from the sun also travels to the cells of green plants (producers) and is stored as energy.

• When light reaches an object, it is absorbed, reflected, or passes through it.

What is light really?Electromagnetic radiation waves

• Light waves are three dimensional

• Light waves vibrate in all planes around a center line.

• The waves have high points called “crests.”

• Waves also have low points called “troughs.”

• The distance from one crest to the next crest is called a “wavelength.”

• The number of waves passing a given point in one second is called the “frequency.”

wavelength

*Electromagnetic Radiation• Electromagnetic radiation can be described in terms of a

stream of photons. Each photon is traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy.

• The only difference amongst radio waves, visible light, and gamma-rays is the amount of energy of the photons. Radio waves have photons with low energies. Microwaves have a little more energy than radio waves. Infrared has still more energy.

• As we move down the chart we see visible, ultraviolet, X-rays, and gamma-rays whose photon energies gradually increase.

• Gamma and Cosmic rays have the highest energy waves.

Remember radio waves are long…and gamma rays are small

Radio-TV -Microwave- Infrared - VISIBLE -Ultraviolet -X-rays - Gamma- Cosmic

Radio(Longest electromagnetic waves)

• Emitted by– Astronomical Objects– Radio Station Transmitters

• Detected by– Ground based radio

telescopes– *If you turn on a radio,, it

will convert the radio wave energy into sound energy.

Television• Shorter than radio, also

used to carry messages (pictures & sound) to our TV sets.

• *We can sense the TV waves around us with our televisions.

Microwave

• Emitted by:– Gas clouds collapsing into

stars– Microwave Ovens– Radar Stations– Cell Phones

• Detected by– Microwave Telescopes– Food (heated)– Cell phones– Radar (systems)

Infrared(Heat or Thermal)

Are you a source of infrared? YES you are!

• Emitted by– Sun and stars (Near)– TV Remote Controls– Food Warming Lights

(Thermal)– *Everything at room

temperature or above,=HEAT

• Detected by– Infrared Cameras– TVs, VCRs,– Your skin

VisibleEach color is a different size wave.

Red the longest & violet the shortest• Emitted by

– The sun and other astronomical objects

– Laser pointers

– Light bulbs

• Detected by– Cameras

(film or digital)

– Human eyes

– Plants (red light)

– Telescopes

Red, Orange, Yellow, Green, Blue, Indigo, Violet (order of colors of the rainbow)

UltravioletSunburn / black light

• Emitted by– Tanning booths (A)– The sun (A)– Black light bulbs (B)– UV lamps

• Detected by– Space based UV

detectors– UV Cameras– Flying insects (flies)

X-ray• Emitted by

– Astronomical objects – X-ray machines– CAT scan machines– Older televisions– Radioactive minerals– Airport luggage

scanners

• Detected by– Space based X-ray

detectors– X-ray film– CCD detectors

Chandra X-ray Observatory• Chandra is designed to

observe X-rays from high energy regions of the universe, such as the remnants of exploded stars.

• The most sophisticated observatory built to date.

• Deployed by the Space Shuttle Columbia on July 23, 1999,

Chandra X-ray Observatory

*Slide from 2004 NSTA Conference

Gamma Ray(Short electromagnetic waves but more energetic)

• Emitted by– Radioactive materials

– Exploding nuclear weapons

– Gamma-ray bursts

– Solar flares

• Detected by

• --Geiger counters– Gamma detectors and

astronomical satellites

– Medical imaging detectors

Sources of g-ray Emission

• Black holes• Active Galaxies• Pulsars• Diffuse emission• Supernovae• Gamma-ray bursts• Unidentified

COSMIC Rays

"Cosmic rays, the highest-energy particles in nature, are thought to be formed when stars collapse and produce tremendous shock waves

• A great question!• Radio waves= (Buildings to human size);• Microwaves

(Humans-beetles);• Infrared waves (Eye of a needle);Visible waves (microscopic size)!

WOW! All the rest are the size of molecules, atoms, atomic nuclei and smaller..

Sensing Light• Humans have two light

detectors.• Do you know what

they are called?

Did you realize cameras and camcorders are light detectors too?

SmartBoard

http://www.exploratorium.edu/learning_studio/cow_eye/video_sm_all.html

http://news.discovery.com/videos/why-tell-me-why-why-is-the-sky-blue.html

There's a face... and the word liar

What do

What do you see?

No, they're both the same size

Is the left center circle bigger?

It's a spiral, right?

No, these are a bunch of independent circles

Keep staring at the black dot. After a whilethe gray haze around it will appear to shrink.

Stare at the black lightbulb for at least 30 seconds.Then immediately stare at a white area on the screenor at a sheet of paper. You should see a glowing light bulb!

How many colors do you see?

There are only 3 colors: White, green, and pink.There seem to be two different shades of pink,but there is only one pink.

Count the black dots! :o)

Are the horizontal lines parallel or do they slope?

How many legs does this elephant have?

Is the blue on the inner left back or the outer left front?

Do you see a musician or a girl's face?