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!

• 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 this question?

1. Why does a person see a flash of lightning before they hear thunder?

Because light travels faster than sound

What happens when light strikes an object

• If light travels through an object it is =transparent

• If light is blocked by an object it is= opaque.

• If some light passes through but not all 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,• 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?Electromagnetic radiation waves

• The waves have highest point is called “crests.”

• Waves also have low points called “troughs.”

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

• The distance from the crest to the trough is the amplitude

wavelength

*A Science Museum of VA:Light Science Activity

What happens when light hits an object?

• Reflects = bounces off an object at the same angle.

• Refracts = light bends when it goes through water.

• Absorbed= light enters an object and stays in the object

Compare and contrast reflection and refraction

Reflection Refraction

Colors

• We have a famous name to help us remember the colors we can see

•ROYGBIV

What Does ROYGBIV MEAN

• R= Red

• O=Orange

• Y= Yellow

• G= Green

• B= Blue

• I= Indigo

• V=Violet

Primary Colors

We can make every other color from the primary colors

Notice the wavelength is long(Radio waves) and gets shorter (Gamma Rays)

Electromagnetic Spectrum

• Radio waves= used for communication

• Microwaves = used for communication and heating food

• Infrared waves = used for heat

• Visible light = allows us to see color

• Ultraviolet waves = produce vitamin D but too much is cancer

Electromagnetic Spectrum Continue

• X-Rays = used to see bones

• Gamma Rays = Help Cure Cancer