Editing Invisible Glass (section)

== Demonstration ==

;Method A:
# Set out the two glass beakers. Fill the first beaker with 400mL of water, and the second with 400mL of Baby Oil. Fill 1-2 test tubes with water and set them in the first beaker. Fill 1-2 test tubes with baby oil and set them in the second beaker.
# As students come by the table, have them note the difference between the two beakers. Ask them why you can easily see the test tube(s) in the first, but not in the second. After they think of ideas, explain the demonstration briefly.

;Method B:
''Note: The jars for this method are already prepared, each with 220 marbles in them (200 small, 20 medium). Skip to step two if you are using the prepared jars.''
# Count out the marbles and put the same number of each size in each jar. Pour water into the first jar, being sure to cover the marbles fully, and put a lid on it. Pour baby oil or corn syrup into the second jar, being sure to cover the marbles fully, and put a lid on it. Be sure to write down the number of marbles you put in each jar!
# Set out both jars, and put out the paper and pencil between the jars. Draw two columns on the paper and label the columns "Water Jar" and "Baby Oil/Corn Syrup Jar".
# As students come up, have them try to guess the number of marbles in each jar. They will find it much harder to guess the number for the baby oil/corn syrup jar than for the water jar. After students write down their guesses, briefly explain refraction, and let them know that both jars have the same number of marbles!