Materials and Light

In this lesson, students carry out two investigations to observe how materials with different properties interact with light in various ways.

• What are sources of light?
• Does light pass through materials the same way?
• What has to happen to be able to see the walls of a dark cave?
• Why aren’t windows made of opaque materials?
• How are transparent materials different from translucent materials?
• Why can you see your image in a mirror?  
• How do mirrors change the light beam from a flashlight?

• What happens to people as we grow?
• How is the way that people grow different from how butterflies grow?
• How did the plants in the last unit grow?
• How is a caterpillar connected to a butterfly?
• What has to happen before a caterpillar can turn into an adult?
• How does the caterpillar change during the pupa stage?
• How does a butterfly look different from a caterpillar?

Misconception: As long as we have eyes, we can see.

Fact: For an object to be seen, it must reflect light. We see different colors and textures because of how light bounces off of different materials and into our eyes.

Misconception: The ability to see is separate from the presence of light. We can sometimes see objects when there is no source of light.

Fact: All sight occurs because of how light reflects off of different objects. Without a source of light, we cannot see.

Opaque: a material that blocks all light

Reflect: to bounce off of

Sight: the sense that uses the eyes to take in light information about an object’s position, shape, and color

Rransparent: a material that light passes through completely

Rranslucent: a material that some, but not all, light passes through

A Reflective Salt Flat

Luca Galuzzi travels the world. He takes pictures of what he sees. On one trip, he stood on top of a giant salt flat. This is a wide-open area covered with salt. When water covers it, this area becomes the world’s largest natural mirror.

Objects Reflect Light

The sky appears to be on the ground. This is because of how the water in the salt flat reflects light. To reflect means to bounce off of. All objects reflect some light. This is how we see them. Light reflects off of the object and into our eyes.

Some objects reflect more light than other objects. Shiny, smooth objects reflect more light than dull or rough objects. Light-colored objects also reflect more light than dark-colored objects.

Some objects reflect light in a way that lets you see images on their surface. This is what happens with mirrors. When you look in a mirror, your image reflects back. It is also what happens with the water in the salt flat.

This lesson has two investigations. In the first investigation, students plan and carry out an investigation to help them answer the focus question: “Does light pass through all materials the same way?” In the second investigation, students explore the focus question: “How do mirrors change the light beam from a flashlight?” Students work collaboratively as a class to develop a procedure that uses the available materials to test their prediction about the answer to the question. Then, students investigate how a flashlight’s beam of light changes when it comes into contact with a mirror.