I began by having students write the date and the focus question, "How can we model how we see things?" in their science notebooks.
Under this question, I asked them to explain, through words and pictures, how we see things. This is an intentionally broad question because I want it to be accessible to my students with the least prior knowledge. After a few minutes, I reminded them of our expectation to speak and listen respectfully, had them share their ideas with their tables.
I structured this lesson by beginning with very simple scenarios involving light and vision, and made each situation increasingly complex. After each scenario, they were to draw how the light travels. I gave my class a great deal of support in the first scenario (we worked on it as a class, they copied it into their notebooks), and gradually withdrew that support until #5, which they completed independently to see if they could apply their knowledge to a new scenario.
Finally, I showed my class Scenario 5 Illustration and explained the following situation: You're walking down a street late at night. There are no lights nearby, but the moon is out. If you were walking under a tree, and couldn't see the moon, but there was a sign just past the tree, could you read it? Why or why not?