I understand that the soap bubble gets thicker at the bottom of the bubble due to gravity, resulting in a complicated array of different colors of different wavelengths being constructively and destructively interfered in different amounts.
However, as can be seen from the image of a vertical soap bubble, the lines get thinner as we go down. My physics teachers told me that "Although the bands are of equal length initially, after a while you hold the bubble up vertically, as the change in the d (thickness of film) gets LESS as you go down where it is thicker, the bands will also get thinner (think of the bubble as a "vase shape")
Doesn't the change in the thickness of the soap film get more harsher as we go down (since gravity pulls the film layer down)? In addition, if the change in the film layer width gets LESS, shouldn't we see bigger bands resulting from the overall similar pattern of different wavelengths interfering? Or is there a better explanation for why the band lines get thinner as we go down?