light and shadows

• Transparent object

  An object that light can pass through
• Transparent objects

  • Glass of water
• Opaque object

  An object that light cannot pass through and changes its path after hitting the object
• Opaque objects

  • Wood
  • Mobile phone
  • Humans
• Translucent object


  An object that allows light to pass through them partially
• Translucent objects


  • Plastic
  • Butter paper
  • Frosted glass
• Shadow

  The light that cannot pass through an object
• You can only see shadows of objects that are visible to eyes
• A tree will have a shadow, so will you and I, but not air and water because light can pass through them
• Multiple shadows

  Depend on the number of light sources
• When the light source is moved away from the object


  The shadow becomes smaller in size
• When the light source is brought near the hand


  The shadow becomes larger
• When the light source is just over the object, you get the shortest shadow
• Size of a shadow

  Depends on the distance between the light source and the object
• Light travels in a straight line and cannot bend or turn around an object to light up the area behind it
• Sun clock


  People used to estimate time using the shadow cast by the earth
• A shadow cast by the earth on the moon results in a lunar eclipse, with the sun as the source of light