Lunar and Planetary Institute

 Children explore light and heat as different components of the Sun’s energy. Invite the children to discuss how our Sun influences us (refer to “About Our Sun”). Prompt them to share their observations. Can they feel the heat? What else does our Sun provide? Is "light" a separate thing from the Sun's heat? Some children may observe that it is warmer and lighter during the day than it is at night — so light and heat from our Sun do not seem to be different things. Others may remember that it can be cold on a sunny day, so it may seem they are different. Invite them to test these two different ideas. Give three small sheets of black poster board to each group. Have them set one aside and use the others to draw and cut out two shapes about three inches across. Be creative — make planets, handprints, or other shapes. Show them the photosensitive paper and explain that this paper darkens when exposed to light. In a few minutes, they will go outside, get a piece of this paper, and  tape their shapes to it. What do they think will happen to the paper under the shapes? Will it turn dark or stay light? How might they determine if it is the Sun's heat or light (or both) that causes the special paper to change? What if they covered half of the photo paper and one of the shapes with black poster board? Will the paper and shape under the poster board be exposed to light? (No) Will it get just as hot as the area not covered? (Yes; it actually will get several degrees hotter because the dark board absorbs more heat.) Before going outside, have the children place several strips of tape around the edges of their shapes as well as the piece of black poster board, in preparation for taping them to the photo paper outside. (The black side of multicolored boards should be the side exposed to the Sun). Invite them to take their shapes outside and prepare to act quickly. Distribute the photosensitive paper. Have them very quickly take the photo paper, tape the shapes on it — a few on each side — then tape the black poster board over one half of the photo paper, including one of the shapes. Wait two minutes and then remove the board and shapes. What do they see? (A clear impression on the side exposed to the Sun’s light and heat, where  the shape blocked the Sun. The rest of the paper darkened where the Sun’s light reached it. There  will be little or no impression on the side covered by the black poster board; that side did not receive light, but it was heated.) As the groups finish have them discuss and record their results. Were the children’s  predictions correct? What does this mean about light energy from our Sun? Is it separate from heat energy? Last updated January 22, 2007 Who? Ages 9 –14 How Long? 60 minutes What's Needed? For each group of 3 or 4 children: • One sheet of 8½” × 11” photosensitive “black and white” paper (from photo supply or science education store) • Pencils • Scissors • Tape • Three 4" x 5" sheets of black poster board • Access to the outdoors and a bright sunny day! Connections to the National Science Standard(s) Standards A,B,&D(grades 5–8):  Communicate an understanding through scientific investigation that the Sun’s energy arrives as light with a range of wavelengths, including visible light and  infrared radiation, and  two ways in which light interacts with matter are  by transmission and absorption. Standards A, B&D (grades 9–12): Understands  through scientific investigation and effectively communicates that light waves have energy and can transfer energy when they interact with matter.  Understands that our Sun is the major external source of energy.