Welcome to a power point presentation on LIGHT.

1
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?

2
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 earths 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.

3
Sensing Light

• Humans have two light detectors.
• Do you know what they are called?

4
How many sources of Light can you list and
explain?

• SUNwarms air,
• water, and land.
• Fireprovides heat, light, and cooking fuel.
• Lightning
• Firefly
• Flashlight
• Light bulb
• Laser beams
• Optical
• telephone
• fibers
• Traffic lights

AIMS Primarily Physics Light Sources Activity
5
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?

6
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 istranslucent.

7
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

8
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.

9
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.

10
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.

11
Lets 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?

12
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
13
Notice the wavelength is long(Radio waves) and
gets shorter (Gamma Rays)