What Are the Facts of Light?

Are you looking for an easy way to teach your child about how light works? We’ve put together a set of free materials that parents and teachers can use right away. In this lesson, your child will dive into the fascinating world of physics.

We’ll explore how light travels in straight lines and the magic behind shadows and pinhole images. Explore science in a more engaging way with captivating 3D videos and interactive quizzes. Download our app to get started!

What You Will Learn From This Lesson

Light travels in a straight line through a homogeneous medium.
Pinhole imaging creates upside-down images through small openings.

How does light travel?

Light is all around us, but have you ever noticed how it moves? Whether it is traveling through the air, water, or even glass, light always travels in a straight line. Scientists say that light moves this way as long as it is in a homogeneous medium—which is just a fancy way of saying a material where the particles are spread out evenly.

A wooden log character blocking light particles to demonstrate how a shadow is formed.

Because light travels in straight lines and cannot “bend” around objects, interesting things happen when something gets in its way:

Shadows: When light is blocked by an object, it cannot go around it. This creates a dark area on the other side, which we call a shadow.
Mediums: Light can travel through many things, including air, water, and even jelly!

The magic of pinhole imaging

Have you ever seen round patches of light on the ground beneath a tree? This isn’t just a random pattern; it’s actually an example of pinhole imaging. When sunlight passes through the tiny gaps between leaves, those gaps act like small holes that project images of the sun onto the ground.

A boy and a yellow character using a candle and screens to demonstrate the concept of pinhole imaging and facts of light.

One of the coolest facts about pinhole imaging is that the image produced is actually upside-down. This happens because light from the top of an object travels in a straight line through the hole to the bottom of the screen, while light from the bottom travels to the top.

You can even make your own pinhole camera at home using simple materials like a cylinder container, black paper, and a thumb pin. By making a tiny hole at one end, you can see the world projected as a magical, inverted image!

Fun Fact

Light doesn’t just travel through air; it can move through water and glass in perfectly straight lines too.
Shadows are basically “light-free” zones created because light is too stubborn to bend around you.
The round light patches under trees are actually “photos” of the sun projected by the leaves.

Vocabulary

Homogeneous Medium: A substance, such as clear air or pure water, where the composition is consistent throughout. This allows light to travel in a predictable, straight path.
Shadow: A volumetric region or surface area of darkness produced when an opaque object obstructs the straight-line path of light rays.
Pinhole Imaging: A phenomenon where light rays from an object pass through a small aperture, crossing paths to project an inverted (upside-down) and reversed image on a surface.
Medium: Any material substance—solid, liquid, or gas—that acts as a carrier for light waves as they move from one point to another.
Straight Line: The fundamental geometric path of light in a vacuum or a consistent medium, a principle known in physics as rectilinear propagation.
Inverted Image: An image that is oriented upside-down relative to the original object, a necessary result of the geometry of light rays in pinhole cameras.
Obstruction: The act of blocking the path of light, which results in the formation of shadows or the redirection of light energy.