Engage: Ask students to close their eyes and imagine the world without sight. How different would your world be? What sights would you miss the most? What daily activities would be more difficult? Would any be impossible? How does the eye help us to be able to see? Explain that today we will be learning about how we see things and how our eyes work.
Explore: Show the video: The Visual System - How Your Eyes Work https://youtu.be/i3_n3Ibfn1c
After viewing the video, have students turn to a partner and ask the following question: "Why is light important when it comes to seeing objects?" (possible response: light is reflected off objects and into the eye.) Lead a discussion explaining that in order for us to see an object, light has to reflect off that object and enter our eyes. We can see in the dark, but there must be a light source such as the moon for us to be able to see objects.
Say, "If you have ever tried to see in a completely dark room before it is very hard to see. If there is no light, we cannot see. Let's do a test to demonstrate this." Place students in groups of 4 students per group. Distribute materials for Seeing in the Dark Activity (one black bag containing small items, and a flashlight for each group). Each group will sit in a circle on the floor. Give each group their black bag containing small objects (make sure none of the students saw you place the objects in the bag before the activity). Dim the lights. Tell the students to hold the opening of the bag close to their face, open it and view the contents, but don't tell any of the other group members what they see. Only allow students a 4-second count to view the objects in the bag as time may become a factor in this activity. The group will pass their bag around the circle for all members to view the contents. Then, as a class, ask, "What objects did you see?" Make a list of any objects the students were able to name on the board.
Say, "Let's see what happens if we add a light source." This time the students will pass the black bag containing the items around the circle holding the bag at arms distance, open it and shine the flashlight inside the bag. Again, they should not yell out any items they are able to see. When all students in the groups have viewed the contents of the bag, ask, "Did you see any objects that you didn't see the first time? Why?" Explain that when there was no light source in the bag, the students could not see the objects inside it. When they shined the flashlight in the bag, they could see the objects because light bounced off the objects in the bag and traveled into their eyes.
Explain: Have students visit the following website: Science Kids How We See (http://www.sciencekids.co.nz/gamesactivities/howwesee.html). Students will play an interactive game using lights and mirrors to control the path of light and illuminate objects. Students will work together collaboratively as a group to decide how to change the mirror to change the direction of the light. Only one computer or mobile device connected to the internet will be needed.
Elaborate: Say, "We need a light source to be able to see, and we know that light reflects off an object and enters our eyes enabling us to see. Now we are going to construct a model to demonstrate how light travels from a light source, reflects off an object and then enters the eye. Remember light travels in a straight line. You will use a ribbon to represent the light, so you will need to make sure when you are holding the ribbon, you pull it tight." Place students in groups of 4 students per group. Distribute the materials: The Eyes Have It Modeling Rubric (one per student, under attachments), a stuffed animal, a mirror, a flashlight, and 4 meters of ribbon. One student in the group should hold the mirror in front of them while another student in the group places the stuffed animal on a table or chair close to the student holding the mirror. A third student will shine the flashlight, while the fourth student represents the "eyes". The student holding the mirror should stand still, but the student representing the eyes may need to keep re-positioning themselves until the stuffed animal is visible in the mirror. All students should be holding on to the ribbon and connecting the ribbon to each object ending with the eye. Some students may need guidance from the teacher to complete this model correctly (There is a sample diagram under attachments for teacher viewing only. Keep in mind student models will vary due to the placement of each element in the model). Distribute chart paper and a marker and ask the groups to draw their model on a piece of chart paper and explain what is happening. Students should use vocabulary and have at least 3 facts on their drawing (example: light travels in a straight line, light reflects off an object and enters the eye, need a light source to see objects).