What is the minimum thickness of a soap bubble that will appear black when viewed in white light?

Practice Questions

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λ/4
λ/2
λ
3λ/4

Questions & Step-by-step Solutions

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Q: What is the minimum thickness of a soap bubble that will appear black when viewed in white light?

Solution: A soap bubble appears black when the thickness is λ/4 due to destructive interference of light reflected from the top and bottom surfaces.

Steps: 6

Step 1: Understand that a soap bubble has two surfaces: the top surface and the bottom surface.
Step 2: When light hits the bubble, some light reflects off the top surface and some reflects off the bottom surface.
Step 3: The light reflecting from the top and bottom surfaces can interfere with each other.
Step 4: If the two reflected light waves are out of phase (they cancel each other out), we see a dark spot, which is black.
Step 5: This out-of-phase condition happens when the thickness of the bubble is a quarter of the wavelength of light (λ/4).
Step 6: Therefore, to see a black color in the soap bubble, the minimum thickness must be λ/4.

What is the minimum thickness of a soap bubble that will appear black when viewed in white light?

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