Yes, there is also a simple derivation in Boys's classic book, "Soap Bubbles: Their Colors and Forces Which Mold Them", p. 136. [1, 2] [1] pdf link (it is out

Yes, there is also a simple derivation in Boys's classic book, "Soap Bubbles: Their Colors and Forces Which Mold Them", p. 136. [1, 2] [1] pdf link (it is out of copyright): http://www.arvindguptatoys.com/arvindgupta/soap-bubbles-boys.pdf http://www.arvindguptatoys.com/arvindgupta/soap-bubbles-boys... [2] google books link (free preview), go to the very last page for the color plate