1) Take around 15 index cards and a flashlight which is opaque on all the sides (so that the light shines only through the front) into a very dark room. After keeping all the 15 cards over beam of light, slowly take out the cards single at a time till you can barely detect the light, and then count the number of cards which remain over the light. After a few minutes, light must begin to look brighter. In this case, add a card and see if you may still see the light. Reiterate this process of progressively adding the cards over a 15-minute period. Specify if you are able to detect an increasingly dim light longer you spent in dark?