LIGHT, SOUND AND FORCE - ESSENTIAL POINTS

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• Light is a form of energy which our eyes can detect.
• Light is made up of electromagnetic radiations; it travels on a straight path.
• Sun is the main source of light.
• We get light from electric bulb, candle, torch and lamp.
• Luminous objects
  • Luminous objects are those objects that give us light out on its own.
  • Examples of non living luminous objects are sun, star and fire.
  • Examples of living luminous objects are fire flies, glow worms.
  • We get to see luminous objects because their light enters our eyes directly.
• Non-luminous objects
  • Non-luminous objects do not give out their own light.
  • Moon is an non living non-luminous object.
  • We get to see non-luminous objects because light is reflected from them and to our eyes.
• When the object blocks the path of light, a dark area is formed on the screen behind the object. This area is called the shadow.
• Sound is formed by vibrations. Vibrations are fast and pro movement.
• When air vibrates, sound is produced.
• When vibrations reach our ears we hear sounds.
• Sound of crackers and horns of vehicles are unpleasant. Such sound is called noise.
• When we push or pull something we apply force.
• Force can stop or move an object.
• Force can change the direction of moving object.
• Natural forces are wind and water.
• Force is pressure applied at an area.