Question

The thinnest bubble film in air that can possibly strongly reflect red light because of constructive interference makes up a certain bubble.
How could we create the thinnest bubble film that will strongly reflect purple light?

• A. Use a thicker film than the film used for the "red" bubble
• B. Use a film with a higher index of refraction than the film used for the "red" bubble
• C. Make a bubble larger than the "red" bubble
• D. Make a bubble smaller than the "red" bubble
• E. Use a thinner film than the film used for the "red" bubble

Answer 1

The correct option is A Use a thicker film than the film used for the "red" bubble

As to obtain a nice coloured pattern, the thickness of the film has to be similar to the wavelength of light and the bubbles are darkest where they are thinnest.