Science Class 3 Light, Sound and Force || Class 3 Science Lesson Light, ...

• We need light to see the objects around us.


• Sun is the ultimate source of light on Earth.


• We also get light from objects like bulb, torch, candle, lantern, oil lamp and table lamp.


• Luminous Objects: Objects that give light.


• Non-luminous Objects: Objects like table, chair etc that do not give light.


• Transparent Materials: Materials like glass, air etc that allow light to completely pass through them.


• Translucent Materials: Materials like frosted glass and butter paper that allow light to pass through them partially.


• Opaque Objects: Objects like wood, bricks etc that do not allow light to pass through them.


• Rays: The straight lines along which light travels.


• Shadow: A shadow is formed when an opaque object blocks the path of light.


• Our Earth moves around the Sun. And the moon revolves around the Earth.


• Earth and moon do not have light of their own. They receive light from the Sun and reflect the light that falls on them.


• Solar Eclipse: On some new moon days the moon comes in between the Sun and the Earth and blocks the sunlight from falling on Earth. A shadow of the moon is formed on the Earth and people in this shadow region cannot see the Sun either totally or partially, for sometime. Such a phenomenon is called a Solar Eclipse.


• Lunar Eclipse: On some full moon days the Earth comes in between the Sun an the Moon and blocks the sunlight from falling on the Moon. A shadow of Earth is formed on the Moon and thus people cannot see moon (partially or totally) for sometime. Such a phenomenon is called a Lunar Eclipse.


• Sound: We hear different sounds around us. We produce sound when we speak or laugh.


• Pleasant Sounds: Soft sounds that make us happy.


• Noise: Unpleasant sounds that irritate us and make us sick. Unpleasant sounds cause noise pollution.


• We should avoid noise pollution by speaking softly, playing music / TV in low volumes etc.


• We do different types of works in our daily life. For doing work we either push or pull something by applying force on it.


• What is force? The push or pull applied on an object is called force.


• Effects of force:
  1. It can move objects.
  
  
  2. It can stop moving objects.
  
  
  3. It can change the shape of an object.
  
  
  4. It can change the direction of a moving object.