Types of light sources:
Natural Light Sources:
The universe is filled with objects that emit light. Some of the light from these sources reach the earth. The following things in nature have the ability to emit light:
Natural Light Sources | Description |
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1. The Sun is the major source of light for the earth. 2. The sun is a massive ball of fire, at the centre of which nuclear fusion produces massive energy. 3. This energy comes out as heat and light. |
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1. Every star produces light. 2. Only a small or no amount of it reaches the earth because of the huge distance. |
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1. The moon provides light as well but it cannot produce light on its own. 2. The light that we get from the moon is the light reflected by it from the sun. |
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1. Some living organisms have the ability to produce light too. It is called bioluminescence. 2. It is the effect of certain chemical reactions within the organism. 3. Fireflies, jellyfish, glow worm, certain deep-sea plants and microorganisms can be cited as examples. |
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1. Certain other natural phenomena such as lightning and volcanic eruptions also emit light. |
Artificial Light Sources:
Apart from the natural sources, light can be produced artificially too.
Artificial Light Sources | Description |
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1. When certain objects are heated to a high temperature, they begin to emit light. 2. Both infrared and visible light is produced in the process. 3. Example- Candle, incandescent lamp. |
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1. Light can be produced by accelerating charges in a luminescent material. 2. One common way of doing it is by passing current through the material. 3. Example- Fluorescent tube light, electric bulb |
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1. Passing electricity through certain gases at a very low pressure can produce light too. 2. Example – Neon lamp, Sodium lamp. |
Light Pollution:
Unwanted extra light from artificial sources is referred to as light pollution. Light pollution exists in four different forms:
1. Glare: This is when a light that is too bright often causes glare, or a visual discomfort, when looking at the light.
2. Skyglow: This is when too many external artificial lights cause the night sky to glow. You can see this when looking down at a well-lit city. The sky above the city is brightened.
3. Light trespass: This is when a big, bright light shining on one area usually intrudes and shines on unwanted areas.
4. Clutter: This is when you have too many lights bunched up together or when the lights are grouped in confusing ways, and it can make you dizzy or confused looking at them.
Effects of Light Pollution:
While many people choose to dismiss light pollution as being the price of modern life, it has serious effects on everything around it.
Interesting Facts:
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