Why do soap bubbles display vibrant coloured bands when illuminated by white sunlight?
Answer and explanation
Correct answer: B. Constructive and destructive interference of light reflected from the front and back film surfaces
- Step 1: Light reflects from both the air-film boundary and the film-air boundary with a relative phase shift. Step 2. Path difference depends on film thickness and angle; specific wavelengths satisfy constructive interference. Answer: Constructive and destructive interference of light reflected from the front and back film surfaces. Why not the others: Dispersion separates colours by refraction, but thin-film colours arise purely from wave interference.
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