Light, Shadows and Reflection
• Light is defined as radiation which is visible to the human eye.
• It helps us see different colourful objects around us.
• The natural source of light is the Sun.
• Sunlight allows us to see objects during the day. It also plays an important role in the growth of plants and in processes such as photosynthesis.
• Luminous objects are objects which emit light of their own. Example: Sun
• Non-luminous objects are objects which reflect light. Examples: Moon, mirrors
Importance of Light
• Light is the main source of energy for animals and plants.
• The sunlight provides natural warmth that creates suitable conditions for the growth and development of life.
• The green plants required sunlight to make their food by the process of photosynthesis.
• The natural colour of light is white, but this white light has seven different colours: violet, indigo, blue, green, yellow, orange and red.
• The objects absorb specific colours of light and reflect the other colours. This reflected colour declare the colour of the object. For example, grass cannot absorb the green colour. So, the green colour is reflected that comes to our eyes.
Image formation by Plane Mirror
3. Answer: We take three pieces of cardboard. Place them one on the top of one another and make a hole in the middle of each cardboard by using a thick nail. Erect these cards up on the table at a short distance away from each other. Take a candle which is of the same height as the holes in the cards. Light the candle and place it in front of the cards. We see that the light of candle is visible only when the holes on cards lie in a straight line. If we disturb them the light of candle disappears. This experiment shows that light propagates in a straight line.