# Problem: 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)?

###### FREE Expert Solution

Constructive interference in thin films (when the film material has a higher index of refraction):

$\overline{){\mathbf{2}}{\mathbit{\eta }}{\mathbf{d}}{\mathbf{=}}{\mathbf{\left(}}{\mathbf{m}}{\mathbf{+}}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{\right)}}{\mathbf{\lambda }}}$

(a)

Refractive index of water, η = 1.33

d = 390 nm (10-9m/1nm) = 390 × 10-9 m

Solving for the wavelength, λ:

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###### Problem Details

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)?