What is the third smallest non-zero thicknesses (in nm) of soapy water ( n=1.33 ) on Plexiglas (n=1.50) if it appears green (constructively reflecting 520-nm light) when illuminated perpendicularly by white light?

the third non zero thickness is t = 586.466 nm

Explanation:

For a constructive interference, the non zero thickness is given by the formula:

Where n = 1.33

m = 3

t = 586.466 * 10⁻⁹ m

the third non zero thickness is t = 586.466 nm

an electric circuit