Light and Sight - Why We Need Light to See

Before/Engage:

1. Show students a nightlight and tell them that you used it when you were their age. (Telling students that you were afraid of the dark will reduce the risk they feel of admitting similar feelings.)  Have students turn and talk to a friend about why they think things look different in their rooms at night.

2. Ask students whether they prefer to sleep with a light on or in complete darkness. Give each student a sticky note to place on the chart paper graph (see Preparation section for details). Once each student has placed his or her note on the appropriate column of the graph, have students to interpret the information by asking questions:

• • How many people in our class like their rooms completely dark at night?  
  • How many people use a nightlight?
  • How many people leave the doors to their rooms open to see a hall or bathroom light?
  • Which way to most people prefer to sleep at night?
  • Why do you think this is the most popular option?
  • If you share a room with someone, do they have the same preference you do? If not, how do you compromise and make a decision?

3. Ask students if they have ever seen something in their rooms that seemed scary in the dark, but when they turned on the light it was not what they imagined. Have students share these experiences with a partner and tell them that they are going to do some investigations today to learn why things look different in the dark.

During/Explore/Explain:

1. Show the 9-minute “Peep and the Big Wide World Night Light” video. Discuss what Peep and Quack have to do to find Chirp in the video (shine a light on him). Ask students what makes a shadow (when the light is blocked by a solid object, it appears darker behind the object). 
2. Explain that an object must reflect light into our eyes or give off light for us to see it. If there is no light, we cannot see the object at all. If there is a little light, we can see a little of the object, but it is not clear. That’s why common objects in our bedrooms sometimes look like scary things at night.
3. Divide students into three groups for exploration at Light and Sight centers:
   • Shadow puppets – Have each student make a shadow puppet by cutting a shape out of cardstock paper and taping it to a craft stick. You may use the patterns provided in the materials section or let students draw their own characters. Students can use a hole punch to make eyes or decorations on their shadow puppets. Students will use flashlights in the “cave” created by sheets over desks to make their puppets make shadows. (Make the entrance to the “cave” facing the teacher so you can monitor student behavior during this center.) Ask students if they think they will be able to see colors on the shadows their puppets make if they color their puppets and have them test their predictions. Challenge students to make their puppets’ shadows bigger, smaller, skinnier, etc. by moving the flashlight and the puppet in different ways.
   • Mystery box -  This group needs a collection of small classroom objects, one flashlight, and the “mystery box” prepared by the teacher before the lesson. Students will take turns putting "mystery" objects in the box and viewing what is inside it. One student places an object in the box while other group members hide their eyes. The other group members take turns looking in the box through the open hole while the flap covering the second hole is closed. (They will not be able to see what is in the box.) Then they will lift the flap to let light in through the second hole and try to identify the object. (The object will be dim but probably recognizable.) Then they will shine the flashlight through the second hole to illuminate the object so it can be seen clearly. Repeat this procedure until every group member has had a turn to place an object in the box.
   • Computer or Tablet Station – Students work individually or in pairs at computers to play the PBS Peep Night Light Game,  Peep Shadow Play Game, and watch the Shifting Shadows video.
4.  After completing all three stations, meet with the whole class to debrief with the following questions:

• • What happened to the shadow when you moved the puppet closer to the flashlight?
  • What happened to the shadow when you moved the puppet farther away from the flashlight?
  • What causes a shadow?
  • When you used the mystery box, when were you best able to see the object inside in order to identify it?  When could you not see the object at all?  Why?
  • Do you see an object better when the light is pointed at the object or at your eyes?  Why?
  • Do shadows appear in different colors?  Why or why not?

After/Explain, Elaborate:

1. Watch Crash Course Moon Phases video. (10 minutes)
2. Turn off the classroom lights and close blinds or curtains. Have the class sit in the center of the room. Explain that they are representing Earth.
3. Ask what they learned about the moon in the video (it travels around Earth). Explain that the ball represents the moon, so you are going to carry it around them. The flashlight represents the sun. Shine the flashlight on the ball so one-half is illuminated.
4. As you walk around the class carrying the "Moon," have students describe what they see at different points in your "orbit." Have students make the connections between the video, the demonstration, and real-life observations of the moon.  
5. Tell students to look at the moon that night and observe how it looks. For the next four weeks, have students report on the appearance of the moon each night and create a T-chart of the date and moon's appearance so students can track the phases of the moon.
6. Have students summarize their learning by drawing and writing an answer to the question, "How does light affect what we see?” on the assessment sheet.