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.
  

 

SOURCES OF LIGHT

• 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
  
  

 

EXAMPLE OF 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.
  

 

EXAMPLE OF 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.
  

 

EXAMPLE OF 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 REALY LIGHT? . .Electromagnetic wave radiation

• 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."
  

 

 

ELECTROMAGNETIC WAVE

• Electromagnetic radiation can be described as a stream of photons. Each photon traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy.
  
• The only difference amongst radio waves, visible light, and gamma-rays is the amount of energy of the photons. Radio waves have photons with low energies. Microwaves have a little more energy than radio waves. Gamma-rays and cosmic rays have highest energy waves and are the deadliest.