What is Light? Reading Comprehension Lesson

Light: A Form of Energy

Light is everywhere, and it allows us to receive information about the world around us. Light comes from many sources, such as fire, light bulbs, and fireflies — and of course, the sun. Without sunlight, there would be only a world of darkness where no plants would grow. Without plants, there would be no food for people or animals, and no heat. Everything would be frozen. Light makes life on Earth possible.

Light is a form of energy that you can detect with your eyes. It is a combination of magnetic and electric energy that travels extremely fast. Light is estimated to travel at the rate of approximately 300,000 kilometers per second. That is so fast that light from the sun, which is about 150 million kilometers away, reaches Earth in only about eight minutes. Nothing in the universe travels faster than light.

Different materials let different amounts of light pass through them. Materials that are transparent — like clear glass — let almost all of the light pass through, so we can see clearly through them. Materials that are translucent — like white paper or frosted glass — let only some of the light pass through, so we can see shapes but not clear details. Materials that are opaque — like a brick wall or a piece of wood — do not let any light pass through, so we cannot see through them at all.

Luminous and Non-Luminous Objects

There are two main types of objects when it comes to light: luminous and non-luminous. Luminous objects are those that emit (give off) their own light. The sun, a fire, a glowing light bulb, and a firefly are all luminous objects. Non-luminous objects do not give off their own light — we can only see them because light from a luminous object bounces off them and travels to our eyes. Books, chairs, and people are non-luminous objects.

The moon is a famous example of a non-luminous object. Even though the moon looks bright in the night sky, it does not give off any light of its own. The moon is simply reflecting light from the sun. As the moon moves around the Earth, different parts of its sunlit side face us, which is why we see different phases of the moon — full, half, crescent, and new. Without sunlight, the moon would be invisible.

Light also reflects, refracts, and creates color. Reflection is what happens when light bounces off a surface, like a mirror. Refraction is when light bends as it passes from one transparent material to another, like water or glass — this is why a straw in a glass of water looks bent. White light is actually a combination of all the colors of the rainbow. When white light passes through a prism, it separates into the colors red, orange, yellow, green, blue, indigo, and violet. Rainbows are formed when sunlight refracts and reflects through tiny water droplets in the air after a rainstorm.

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