Question:medium

Two children observe soap bubbles in sunlight. Initially the bubble appears bluish, but after some time it turns yellowish.
Which of the following statements are correct?
I. The colour shifts towards higher wavelength.
II. Blue/violet colours disappear earlier than red.
III. For sufficiently thick bubbles, the bubble appears white.

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For thin-film interference, remember the relationship: thickness is proportional to the wavelength for constructive interference ((t propto lambda)). Thinning film (like a dying bubble): Color sequence shifts from red (to) yellow (to) blue (to) black (destructive interference for all wavelengths). Thickening film (like a newly formed bubble settling): Color sequence shifts from blue (to) green (to) yellow (to) red. The question describes a bubble thinning over time, so the color shift is towards red, but eventually all colors disappear starting from blue.
Updated On: Apr 19, 2026
  • I and II only
  • II and III only
  • I and III only
  • I, II and III
Show Solution

The Correct Option is D

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