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Grade 3 | Science | Light, Light, Sound and Force, Olympiad, CBSE, ICSE, Maths Olympiad, Science Olympiad, English Olympiad
LightWe see with our eyes but we cannot see anything when there is no light. We have noticed that in complete darkness no object is visible to us. So, let's understand what is light. It is a form of energy which is important to us. Without light, plants can't make their food and if plants don't their food, we won't get anything to eat as well.
Light is always emitted from a source. There are two types of sources of light-
1. Natural
2. Artificial
Natural source of light-
Sun is the main source of natural light. Natural light is also emitted by the other stars and moon. Star provides very less amount of light at night because they are very far from the earth compared to the sun. The light from the moon is just a reflection from the sun and it provides very less amount of heat and light to us at night.
Artificial light is produced by burning wood, candles, lamps. The electric bulbs and lamps are also a source of artificial light.
Luminous bodies are those which emit light of their own such as sun, stars, and bulb. Non- luminous bodies are those which do not have their own light such as the moon, book, etc. The non-luminous object is visible to us when light from the luminous object falls upon it.
Characteristics of light:-
1. Light travels in a straight line in the form of rays.
2. It travels very fast at the speed of 300,000 km in a second.
3. Light does not bend, it can only be blocked.
4. Light continues to travel in a straight line until it hits something else and this causes the formation of the shadow.
Shadow
Shadow is formed when light is not able to pass through an opaque object. When an opaque object comes in the path of the light, the light falling on that object cannot reach the other side, therefore, that particular region becomes dark.
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