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What is Light?

Last updated date: 29th Feb 2024
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Overview of Light

We are surrounded by light. In addition to allowing us to see in the dark, light's unique attributes are crucial to many elements of our life. We are kept safe by reflections in the rearview mirrors of moving vehicles. Some people can see better, thanks to refraction through contact lenses or eyeglass lenses.

We can communicate with our TVs by sending pulses of infrared light as signals and listening to radio broadcasts too via EM waves. The focus of this backgrounder is on visible light and our interactions with it. You will learn the definition of light in this article, along with some fascinating information about light.

What is Light? 

Light is an electromagnetic radiation that the human eye can perceive. From radio waves with wavelengths measured in metres to gamma rays with wavelengths shorter than around 1 x 10−11 metres, electromagnetic radiation occurs throughout a very broad range of wavelengths. Luminous objects emit light, which is a type of energy. Luminous items include the Sun, a bulb, a candle, etc. Non-luminous items are other objects that do not emit light. Translucent materials can let light through them faintly.



Sources of Light for Kids

One can say that there are many sources or types of light. But primarily, they are categorised under: 

Natural Source

Look around yourself, you will find numerous natural sources that emit light. Let us talk about certain sources in nature that give us light. Natural source of light examples include the following:

  • Sun: It is the primary source through which we get natural light. It is an enormous ball of fire that produces tremendous energy. This energy further reaches us as light and heat. 

  • Stars: Every star generates light too. But as the distance between the stars and the earth is quite huge, only a small amount of light reaches the earth.

  • Moon: Though the moon does not produce light on its own, the light we get from the moon is reflected from the sun.

  • Some living organisms also produce light, like fireflies, jellyfish, and glow worms. This is called bioluminescence because of certain chemical reactions with these microorganisms.

  • Natural phenomena like volcanic eruptions and lightning also give us light.

Artificial Source

Of course, we get light from natural sources, but there are certain man-made sources from which light is produced. They are:

  • Incandescent Sources: When we heat an object at a high temperature, it can emit light. E.g. candles

  • Luminescent Sources: When we pass a current through the material, light can be produced. E.g. electric bulb, tube light

Properties of Light 

The speed of light in a vacuum (a space devoid of air) is about 299,792,458 metres per second (m/s). The term "light speed" refers to this value. It can move at the speed that nothing else in the universe can! In contrast, the sound wave travels at only about 300 m/s per second. Due to this, lightning is usually visible before thunder in a storm. 

  1. Transparent objects allow light to pass through them and pass through to the other side. We can, therefore, see through translucent objects.

  2. Most of the light that strikes rough, opaque materials is absorbed and converted to heat energy. Light is primarily absorbed by a black surface.

  3. Light reflects off of a glossy, smooth surface in a certain way when it hits it. This is how we are able to see ourselves in the mirrors.



Colours of Light 

Light is mostly composed of the colours red, green, and blue. Yellow, magenta, and cyan are the secondary colours of light. Red, blue, and green lights are used in varying proportions on computer screens to create all the colours you see. White light is made up of the seven colours of rainbow, when the primary colours of light are blended.

Different Colours Obtained From White Colour

Different Colours Obtained from White Colour

How Do Humans Perceive Light? 

Non-luminous items that are exposed to white light reflect some colours while absorbing the others. The colour of light that an object reflects determines its colour. If an item reflects red light and absorbs all other colours, it appears red.

Three different types of photoreceptor cells, each sensitive to long, medium, and short wavelengths of visible light are used by the human eye to interpret colour. For instance, the perception of yellow light wavelengths is the same as that of red and green light combined.

This is due to the similar stimulation they provide for the cells in the eye. In other words, whereas pure yellow light and a mixture of red and green light are physically distinct, we see them both as yellow. 

Yellow Light Appearance

Yellow Light Appearance

Interesting Facts About Light 

Light is a form of energy. Light waves travel in straight lines away from the light source until the waves hit something. Below are interesting facts about light. 

  • Humans are unable to see portions of the electromagnetic spectrum that other animals can. For instance, many insects are capable of seeing ultraviolet (UV) light.

  • The human eye cannot see infrared light as its wavelength is too long.

  • In the field of optics, a subfield of Physics, researchers investigate the characteristics and behaviours of light.

  • Light takes 1.255 seconds to reach the Moon from the Earth.

  • Glass, water, and air are some of the different media where light moves more slowly.


The light is comprised of different colours. The colour which is visible to humans is reflected while others are absorbed by the object. It showed the mechanism of how humans perceive light and distinguish colours. We also know that light is a form of energy. It travels in straight lines. Light waves travel in straight lines away from the light source until the waves hit something.

FAQs on What is Light?

1. What is light? What is the speed of light?

The region of the electromagnetic spectrum that the human eye perceives as light, or visible light, is made up of electromagnetic radiation. Electromagnetic radiation occurs over a very wide range of wavelengths. Photons are bundles of the electromagnetic field that carry a set amount of energy and are the building blocks of light. In vacuum (a place devoid of air), the speed of light is approximately 3x108 metres per second (m/s).

2. Can light move in a vacuum? How does the speed of light differ with different mediums? 

Particle-wave duality is a feature of photons in light. They can act both like particles and like waves. As a result, light does not need a medium to propagate. It is capable of traversing a vacuum. In a vacuum, light moves at a constant speed. Because different photons have different energy, their magnetic and electric fields also oscillate at various speeds. While all forms of light travel at the same speed in a vacuum, different media might have varying speeds. The speed and wavelength of a light wave decrease when it passes through a denser media, such as glass.

3. On which theory nature of light depends?

The nature of light depends upon both wave theory and particle theory.