The excess pressure inside one soap bubble is three times that inside a second soap bubble, then the ratio of their surface areas is

1) 1 : 9

2) 1 : 3

3) 3 : 1

4) 1 : 27

5) 9 : 1  

White light is shining on the surface of a soap bubble, which has the same index of refraction as water. Find the minimum thickness, in nanometers, of a soap bubble that appears red (a wavelength of 725 nm) when the light is perpendicular to its surface.

A soap bubble is essentially a thin film of water surrounded by air. The colors you see in soap bubbles are produced by interference. 

(a) What visible wavelengths of light are strongly reflected from a 390 nm -thick soap bubble? 

(b) What color would a 390 nm thick soap bubble appear to be (green, purple, or yellow)?

A spherical soap bubble with a surface-tension of 0.005 lbf/ft is expanded from a diameter of 0.5 in to 2.0 in. How much work, in Btu, is required to expand this bubble?