這個專題研究的目的是要發展出一套簡單可靠的方法和廉價自製的器材，在地面上即能有效估測大氣層的厚度。我們小組研究光學中雷氏(Rayleigh)散射的原理，針對空氣分子對光線散射作用和特定方向之偏極效應，利用一已知散射長度之路徑，測量其偏極光的強度，同時比對由大氣層散射而來，在同一偏極面上的散射光強度，即能估算大氣層的厚度，方法簡單新穎，自製器材經實際測量和改進，有發展和推廣的價值。\rThe main idea of the experiment is to set a system in order to effectively estimate the thickness of the atmosphere. On the theory of “Rayleigh Scattering” (small air molecules sizing about 10-4μm), we developed an equipment that has two tubes. The tubes lead the scattered lights from two paths. One is called “air light” scattered in the ground air, and the other “sky light” is scattered in the sky and reflected by a beam splitter. The two paths are on the same plane; the scattered lights are perpendicular to the direction of sunlight and 100% polarized. We could adjust and measure the distance “d” of the air light path. We simultaneously observe and compare the intensity of the lights from the two paths with the electronic instrument made by ourselves. By using the known distance “d” and the reflection “x” of the beam splitter, we can calculate the thickness of the atmosphere. The experiment is simple, novel and easy to do in an extensive field at school. Researchers don’t have to use a bloom, radar or satellite to discover the atmosphere, but you could use a simple equipment to observe the features of it.