Light

How do you LIGHT Up

your world ?

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, and 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.

Sensing Light

• Humans have two light detectors.

• Do you know what they are called?

How many sources of Light can you list and explain?

• SUN=warms air, water, and land. • Fire=provides heat, light, and

cooking fuel. • Lightning= • Firefly= • Flashlight= • Light bulb= • Laser beams= • Optical telephone fibers= *Traffic lights=

*

Can you answer these 6th grade questions?

• 1. A person will see a flash of lightning before they hear the thunder that goes with it because?

• 2.Can you draw a long wavelength and a short wavelength next to it?

• 3. Can you contrast objects that are transparent, translucent, and opaque?

“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.

Let’s find out how light travels?

• Simple Activity: 1 working flashlight

• 1. Shine a flashlight on a wall.

• 2. Does light from the flashlight reach the wall? How do you know?

• 3. What evidence do you have showing light travels in a straight line?

• 4.Move closer with the flashlight. Any changes?

What is light really? Electromagnetic radiation waves

• 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