Light

In this lesson, students explore the cause-and-effect relationship between light and our ability to see. Students begin by investigating how objects need to be illuminated in order to be seen and then explore the effects of placing objects with different properties within a beam of light.

• Hearing is one sense that humans and many animals have, and sight is another sense.
• Objects can only be seen when they are illuminated, and this illumination can come from another source, such as the sun, a flashlight, or a lightbulb shining on other objects, or from self-illumination, when objects make their own light.

• How does your sense of sight change if you’re in a room that is completely dark?
• What has to happen to see the objects in the room?
• Have you ever been in a place that is completely dark, where there is no light?
• Using one of the places referenced in the last answer, what would have to happen to be able to see in that space?

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

Transparent : a material that light passes through completely

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

Exploring Caves

Dave loves to explore caves. Caves are large open spaces under the ground. One cave is deep beneath the desert in New Mexico. Dave used a rope to lower himself into the cave. It got darker the farther down he went.

Lighting Up Objects

Before long, Dave was surrounded by darkness. He could see only the rope in front of him. He could see headlamps on. the rope because he had a headlamp.

His headlamp lit up whatever was in its beam of light. This light let Dave see the things in front of him. Sight is a sense. It uses the eyes to take in light information about an object’s position, shape, and color.

Seeing in a Cave

We can only see objects when there is light. Caves are dark places. This is because they are underground. Light from the sun doesn’t reach them. When Dave first enters a cave, there is some light. This light is from the sun. The farther he moves into the cave, the darker it gets.

In this lesson’s hands-on activity, students conduct an investigation to help them answer the focus question: “Why can’t you see well in the dark?” Students investigate to see how well they can see the figurine inside the cardboard tube when all light is blocked, some light is blocked, and a little light is blocked. They use their observations from the investigation to construct an explanation about the relationship between illumination and sight. After the investigation is complete, students present their analysis to the class and discuss the cause-and-effect relationship between sight and light.