A soap film is viewed in white light. If the film is much thinner than the wavelength of blue light, what is the appearance of the film?

Question

The soap film appears totally transparent because it reflects no visible light.
The soap film appears blue because all others colors are transmitted.
The soap film appears white because it reflects all wavelengths of visible light.
The soap film appears red because all other colors are transmitted.

Please explain

Answer 1

I wonder what "much thinner" means. I was yesterday much thinner than today.

If it is really much thinner than blue wavelength, the blue and greens will be canceled by interference and the appearance will be magenta...close to red some would say.