Lesson Two: The Cloud Chamber

The Cloud Chamber While radiation cannot be seen, the cloud chamber allows you to see the tracks it leaves in a dense gas. Materials small transparent container with transparent lid flat black spray paint blotter paper pure ethyl alcohol radioactive source masking tape dry ice styrofoam square flashlight gloves or tongs to handle the dry ice First, paint the bottom of the container with black paint and let it dry. Then cut the blotter paper into a strip about as wide as the height of the container. Cut two windows in the strip, as shown, and place it against the inside of the container. Directions: Pour enough ethyl alcohol into the cloud chamber to cover the bottom of the container. The blotter paper will absorb most of it. Place the radioactive source in the cloud chamber and seal the lid with tape. Place the cloud chamber on the dry ice to super-chill it. Wait about five minutes. Darken the room. Shine the flashlight through the windows of the chamber while looking through the lid. You should see "puffs" and "trails" coming from the source. These are the "footprints" of radiation as it travels through the alcohol vapor. The vapor condenses as the radiation passes through. This is much like the vapor trail left by high flying jets. Do you see radiation in the cloud chamber? ________ Other Ideas To Explore Try to identify these footprints: •Alpha: sharp tracks about 1 cm long •Beta: thin tracks 3 cm to 10 cm long •Gamma: faint, twisting and spiraling tracks Caution: Dry ice should be handled very carefully! It can burn unprotected skin.