Methods of Detection - Case Notes

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Author: Scott Davis - Summer 1998

Background: Many students do not realize that scientists do not actually see the objects that we investigate. We determine its presence by a technique other than vision. In the very simplest form, we "feel" its presence. Some examples include Rutherford scattering (presence of the nucleus), water tank experiments (presence of the neutrino), and the Milliken oil drop experiment. Therefore, the ability to indirectly detect an object is of paramount importance in the sciences.

Teaching Notes:

Exercise 1. In this experiment, the students will hear and feel the presence of the objects contained in shoeboxes. Prepare sealed shoeboxes containing items that can move freely. Some objects include balls of varying sizes, a dowel, a block, and a cone. The students test each box and their predictions will be compiled and discussed. Each group will test each box and the results will be compared for each system.

Exercise 2. In this experiment, students will mimic atomic force microscopy with the use of pickup sticks and the shoebox. This shoebox should contain different objects glued to the bottom. Students use the pickup sticks to determine the shape and plot this surface. Each group is given one pickup stick and allowed to punch holes in the boxes. The number of punches are increased, up to fifty. The student groups present their surface determination. The boxes are then opened and the contents compared to the sketched drawing. This method can be related to atomic force microscopy.