Index of Refraction

This is a classical experiment that is also traditionally performed in a laboratory. Today with the availability of all sorts of transparent plastic boxes (tanks) the experiment can be easily done at home. Photo shows the set-up. Pins, tooth-picks, pencils, or drinking straws could be used as markers. A rectangular box made of transparent plastic can be found in every home. With some water in it, a tank can serve the same purpose as glass blocks used in the school laboratory. Working with liquid it is very easy to estimate the ratio of real depth to apparent depth.

Keep a straw vertically, touching one side of the tank (fix it wit a sticky-tape). Looking at the straw from the opposite side with the eyes at water level try to match another straw with the image of the first one as seen through water. Here one may need the help of another person. When the two indicators seem to be in the same position, "the assistant" should measure the distance between the pegs. This way we know two distances: a real depth of the block Dr and the apparent depth Da We determine the index of refraction of water from the formula:

n = Dr/Da