Why RED BUBBLES are impossible… or are they?!

@Physics Girl  Hi Dianna!  I'm glad you made a video about soap bubbles and color, which is one of my favorite things.  But guess what.  You *can* get red in a soap bubble with white light.  You just need a certain light source.  Specifically the common *triphosphor fluorescent* light bulbs or tubes.  I actually used Kaleidagraph to graph the intensity of the colors in thin soap films, based on the mathematics of interference (adding sine waves together with a phase shift).  I have actually been able to accurately predict the colors in the soap bubble all the way out to 1500 nanometers or so, and the colors repeat after about 1600 nanometers.  This is assuming the fluorescent light illumination, and a refractive index of 1.35 for the film.  At about *800-850 nanometers,* there is a spot where the 611.5 nanometer spike, and 630 nanometer area of the fluorescent light add together, and most other colors, except one peak at 488 nanometers, cancel.  This creates a red-like color I like to call "interesting red".  So there's actually no reason that you can't get red in a soap bubble.  You just need a light source with *discrete* emission spectra (rather than the continuous incandescence of the sun and light bulbs).  And as long as those wavelengths are in the right place, red can appear.  It's really cool!  Thanks for the great video, and talking about something I've found fascinating for a long time!