What is Light?
Light is one of the most fascinating things in the universe — it lets us see everything around us, from the words on this page to distant stars millions of kilometres away. But what exactly is light?
A form of energy that travels as an electromagnetic wave and can be detected by the human eye. It does not need a medium (like air or water) to travel through.
Light belongs to a large family called the electromagnetic spectrum. Unlike sound waves, which need particles to vibrate, light can travel through the vacuum of space. This is why we can see the Sun — its light crosses 150 million kilometres of empty space to reach us!
Think of throwing a ball across a room — the ball needs air and gravity to travel. Light is different: it's more like a ripple in an invisible field that can travel even where there is nothing at all.
Sources of Light: Luminous vs Non-Luminous Objects
An object that produces its own light by converting energy (such as heat or electricity) into light energy.
An object that does not produce its own light but can be seen because it reflects light from a luminous source.
Examples of luminous objects include:
- The Sun (nuclear energy → light)
- A light bulb (electrical energy → light)
- A candle flame (chemical energy → light)
- A firefly (chemical energy → light)
Examples of non-luminous objects include:
- The Moon (reflects sunlight)
- A book (reflects light from a lamp)
- Your skin (reflects light from the Sun or a light bulb)
Many students think the Moon produces its own light. It does not! The Moon is a non-luminous object — it simply reflects light from the Sun. That's why we see different phases of the Moon as it orbits Earth.
10 more sections in this topic
Pick this up in your Library: it holds the whole topic, notes, cheatsheet and questions.