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4. A soap bubble with n-1.33 is illuminated by white light and produces constructive interference for a wavelength of 460 nm. The bubble is in air and is filled with air. a. Sketch the situation indicating where the light is reflected and what the indices of refraction are at each reflection. (You don't need to sketch the entire bubble.) b. Is the reflected wave inverted at the air-to-bubble interface? Explain. c. Is the reflected wave inverted at the bubble-to-air interface? Explain. d. What is the minimum thickness of the bubble to produce constructive interference for this wavelength? What wavelength destructively interferes at this bubble thickness? e.

Answer 1

Part(c). As wave 1 is traveling in water and is reflected on a medium having smaller index(air) , so wave is not inverted and undergoes phase shift 0.

Part(c). As wave 1 is traveling in water and is reflected on a medium having smaller index(air) , so wave is not inverted and undergoes phase shift 0. (b) As wave (2) is travelling in air and is reflected on a medium having a larger index of refraction (water), the wave is inverted and undergoes a phase shift pi. part (d) minimum value of thickness (rho_min) = lambda_0/4n = 460 nm/4 times 1.33 rho_min = 86.466 nm Ans.