Posted by ingrid on .
* Take about 15 index cards and a flashlight that is opaque on all sides (so that light shines only through the front) into a very dark room.
* Place all 15 cards over the beam of light.
* Slowly remove the cards one at a time until you can barely detect the light, and then count the number of cards that remain over the light.
* After a few minutes, the light should begin to look brighter. When this is the case, add cards and see if you can still see the light.
* Repeat this process of gradually adding cards over a 15-minute period. Were you able to detect an increasingly dim light the longer you spent in the dark? Record your reaction.
* How many cards did it take to not see the light after time?