What is Light – Definition, Function, Characteristics, Sources, Speed

‘What is light’ along with its definition, basics, examples are covered in this session. Let’s explore the details!

What is Light? 

Light is the most common term which we all know in our day to day life and it’s really very interesting. Now, what is light? 

In the daytime, we see everything around us due to the sun, and night time, we can not see anything unless we switched on our lamp or tube light or bulb or lit a candle.

So, we can say, if the light is present, we can see around us and if the light is not present, we cannot see anything. Hence, light helps us to see things around us. 

Light Definition

Hence, we can say, Light is energy which helps us to see things around us. This is the simple definition of light for kids.

The function of Light – Why is light so important?

Every day, we wake up when the sun rises, and the light falls on us. We do all our activities in the presence of light. We read books, we play with friends, we see things, we go to school and all other activities in the presence of light.

Plants make food in the presence of light and we take that food and survive. If the light is not present, plants will not be able to make foods and we can not survive.

Hence, the main function of light, are as follows:

• Visibility: To See things around us
• Activity: To do all activities
• Survival: To survive in the world

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Kinds of Light – What Are The Different Kinds of Light?

We wake up when the sun rises. Sun is the ultimate source of light. At night, we switched on the tube light and do our study. So, apart from the sun, there are various kinds of light we get through. So, kinds of light shall be as follows:

• Sunlight
• Stars
• Light from the bulb
• Light in the signals
• Candle
• Matches 
• Torchlight
• Tube light
• Lamp
• Light in the car
• Laser light
• Fire
• Light from fireflies
• Light from electric fish, jellyfish
• Lightening
• Light from volcanos etc.

Source of Light

Source of Light definition

Light is coming from various sources and these sources are known as sources of light. There are many lights which are natural which means these are not man-made and in the same way, so many lights are not natural which means man-made.

How many sources of light are there?

Based on the type of source, sources of light are classified into two categories:  

• Natural Source 
• Artificial Source

Natural Source of Light and Examples 

Natural Source of Light

If the source of light is natural, then it is known as the Natural Source of light.

• This source is natural.
• This source is not manmade
• The sun is the main source of energy. It’s a very big ball of fire and emits fire as well as light. Hence, it’s a natural source of energy.
• There are some living organisms also produces light because of certain chemical reactions within their body like fireflies.
• Lightening, electric fish, volcanos also natural sources of light.

Examples of Natural Source of light

• Sun
• Stars
• Electric fish
• Jellyfish
• Lightening
• Light from volcanos

Artificial Source of Light and Examples

Artificial Source of Light

If the source of light is not natural and instead of natural it is manmade, then it is known as an Artificial Source of light.

• This source is not natural.
• This source is manmade
• Torch, bulb, etc. are not natural. These are the manmade sources of energy, so these are the artificial sources of light. 
• There are wide verities of artificial lights in the world.

Examples of Artificial Source of light

• Light from the bulb
• Light in the signals
• Torch light
• Tube light
• Light in the car
• Laser light

Speed of Light

What is the speed of Light?

Do you have a bicycle? Do you know you can control the speed of it? You can make it faster or you can be slower too. Whatever, when you ride the cycle, it will have speed.

In the same way, light is also having a speed. However, this speed is fixed, and we can calculate also.

Speed means distance travel in 1 sec or 1 hour. 

• In the below picture, light travels 150,000,000 km in 500 sec.
• So, we can say, in 500 sec light travel 150,000,000 km
• or in 1 sec light travels = 150,000,000/500*1 = 300,000 km/sec

Speed of light units

• Hence, we have already seen, speed of light is 300,000 km/sec.
• If we convert, the speed of light in meter/sec, it will be 300,000 x 1000 meter/sec or 3 x 10⁸ meter/sec.
• If we convert, the speed of light in mph, it will be 671,000,000 miles/hours.

Source of Light Images

Natural Source of Light Images

Sunlight	Stars	Electric Fish
Jellyfish	Lightening	Light from Volcanos

Artificial Sources of Light Images

Torchlight	Tube Light	Light in the signal
Bulb	Laser	LED

Light & Vision – How Does Light Affect Vision?

Relationship between light and vision. We already discussed, if the light is present, we can see and if not present, we cannot see. Now, if I ask you to show a bird that it is an elephant, how do you explain that it’s not an elephant, it’s simply a bird?

What will we do? We will see first by our eyes and the eyes will send a signal to the brain and the brain will specify that it’s not an elephant, it’s a bird only.?

Hence, vision constitutes considering the main three things:

• Light
• Eyes
• Brain

There are many people who are blind, they cannot see things. Although, there are several examples of highly educated, highly skilled persons who are blind in our nations.

Further Study

Reference

• NCERT Books
• Study Windows Experience

Conclusion

Hence, we have got an idea of what is light! Do you have any questions? Please feel free to contact us. Thank you for visiting.