What Is Light?

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Objective

Students will understand what light is and what the visible light spectrum is.

Big Idea

Visible light spectrum

RAP - Review and Preview

5 minutes

I call students to the gathering area. I tell than that we will be starting to learn about a whole new field of science, called Neuroscience. Neuroscience is the science of how our nervous system is made and works. Our nervous system is the information system of our bodies. It is the way our brain communicates with the rest of our bodies. We will look at how animals process light, through their eyes, and how this process occurs. However, in order to understand some of the concepts of Neuroscience, we will need to do some physics to understand the basics of light.

I ask students if they know how rainbows are formed? Some will be able to tell me that a rainbow is white light, split into its spectrum. Some will be able to tell me that it is formed by light and water in the air. Some will have little understanding of how a rainbow is formed.

I tell students that we will look at white light (like sunlight) and how we can break it up into the colors we see in the rainbow. 

Demonstration

20 minutes

As a class, we observe the colored spectrum as we bend light through a prism or reflect it through water, with a mirror. This produces our own rainbow!

Note: There are two ways to do this:

  1. If you have access to a glass prism, you can use a flashlight or bulb as a light source and shine it through the prism to refract and break it into its component parts. Place the prism in front of a piece of paper or screen to project the colors.
  2. If you do not have a prism, you can refract light by using sunlight. Fill a pan or bowl 2/3 full of water. Place it on a table or floor in direct sunlight (Direct sunlight is important for this to work). Hold a mirror underwater, facing towards the sun. Hold paper in front and above the mirror. Adjust the position of the mirror and paper until the reflected light shines on the paper. Observe the colors.

Once we have observed the rainbow in our classroom, I ask students what this tells us about light? Most students will look blankly at me. I usually have at least one student who is brave enough to hypothesize that white light is made up of other colors. Usually they have no explanation for this though.

I tell students that light is made of waves. Visible light, the light that we see, is a small part of the electromagnetic spectrum. I walk them through the PowerPoint, explaining what light is and how it acts in the environment. It is not important at this point to understand the wave properties of light, because this will be explained in an upcoming unit on waves.

 

Independent Investigation

10 minutes

My students often like to revisit the information I give them on a new topic. Therefore, I have begun making some of my PowerPoints into videos for them to access later. I don't like to just hand out my PowerPoint to students as they often mess around with them, so I make them into videos and upload them to my Google Classroom or to a shared folder on our school intranet.

Wrap Up

5 minutes

Students complete an exit ticket about the different colors of the spectrum and match definitions and terms covered in the PowerPoint.