How do you LIGHT UP

your world ?

5.3 Light

Welcome to a power point presentation on LIGHT.

• We will investigate the following:• 1. What is light?• 2.What are some sources of light around us?• 3. What are opaque, transparent, & translucent objects?• 4. What is a light wave?

Light

• 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.

How many sources of Light can you list and explain?

“Just Passing Through:” What happens when light strikes

glass? Or waxed paper? Or a book?

• If light travels through an object it is =transparent

• If light is blocked by an object and a dark shadow is cast it is= opaque.

• If some light passes through but not all and a light shadow is present it is=translucent.

What happens when light hits these objects?

• Glass of water • School bus window• Notebook paper• Waxed paper• Plastic wrap• Tissue paper• Cardboard• Textbook• Hand lens…

Transparent objects:

• The windows on a school bus,• A clear empty glass,• A clear window pane,• The lenses of some eyeglasses,• Clear plastic wrap,• The glass on a clock,• A hand lens,• Colored glass…• ALL of these are transparent.

Yes, we can see through them because light passes through each of them.

Translucent objects• Thin tissue paper,• Waxed paper,• Tinted car windows,• Frosted glass,• Clouds,• All of these materials

are translucent and allow some light to pass but the light cannot be clearly seen through.

Opaque objects:

• Heavy weight paper,• Cardboard• Aluminum foil,• Mirror, bricks, buildings,• Your eyelids and hands,• Solid wood door,• All of these objects are

opaque because light cannot pass through them at all.

• They cast a dark shadow.

What is light really?

• 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

Don’t’ forget…longest waves (radio) ..to shortest waves (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

UltravioletSunburn / black light

• Emitted by– The sun – Tanning booths – Black light bulbs – 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

Gamma Ray

• Emitted by– Radioactive materials– Exploding nuclear

weapons– Gamma-ray bursts– Solar flares

• Detected by• --Geiger counters

– Gamma detectors and astronomical satellites

– Medical imaging detectors

COSMIC Rays(The highest energy waves and the deadliest)

• Cosmic rays come from deep space and can pass through the Earth.

Lewis Latimer

• African-American• Lived from 1848-1928• Invented a long-lasting carbon filament

that made the light bulb more useful.• He also patented a threaded wooden

socket for light bulbs and supervised the installation of electric streetlights in New York City, Philadelphia, Montreal, and London.

Isaac Newton

• English• Lived from 1643-1727• Discovered that white light was not a

simple entity, but splits into a range of colors

• When he passed white light through a glass prism, he noted that a spectrum of light was formed; particle theory of light

• Reflecting telescope

Anton van Leeuwenhoek

• Dutch; born in Holland• Lived 1632-1723• Made over 500 simple microscopes• Discovered bacteria, free-living and

parasitic microscopic protists

Galileo Galilei

• Italian• Lived from 1564-1642• Developed the refracting telescope• Developed the first known example of the

microscope

Robert Hooke

• English• Lived from 1635-1703• Devised the compound microscope and

illumination system• Discovered plant cells• Examined fossils with a microscope