Thin Film Interference (part 1)
by Super User, 9 months ago
At about 1:20, the colors seen in the upper section of the ring are roughly what we would expect from a linearly increasing film thickness. Meanwhile in the lower section the thickness is changing in a more complicated way, and the colors appear washed out.
The soap film shown here consists of 2/3 cup of Dawn liquid dishwashing soap, 3 tablespoons of glycerol, and 1 gallon of water. We guess that the average index of refraction of the solution is close to that of water (about 1.33). The footage was taken July 16, 2014—the third consecutive day of rain and high humidity in Cambridge, MA. The light source is a portable fluorescent light box with a color temperature of between 4500 and 5000 Kelvin.
The camera used is a Blackmagic Cinema MFT with an Angenieux 20-80 mm zoom lens. The footage was shot at 800 ASA in CinemaDNG RAW 2.5K and color corrected using DaVinci Resolve 10 Lite.
For further study, see
Physical Science Study Committee, Physics, (D.C. Heath, 1960) Chapt. 19 sect. 9 "Interference in Thin Films.”
Leslie J. Atkins, Richard C. Elliott, Investigating thin film interference with a digital camera. Am. J. Phys. 78, 1248 (2010); http://scitation.aip.org/content/aapt/journal/ajp/78/12/10.1119/1.3490011#