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Transcript
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?
• 5.Are there any hands-on/minds-on activities I can
do to learn more?
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=
*AIMS: Primarily Physics:
Light Sources Activity
Can you answer these 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.What scientific tools are used to study light?
4. 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: 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
• 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
Notice the wavelength is long(Radio waves) and gets shorter (Gamma Rays)