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Thin Film Interference - Example 3

Thin-film interference is the interaction of light waves reflected from the top surface of a thin film with light waves reflected from the bottom surface. The reflected waves combine to form a pattern of light and dark bands (or fringes) called an interference pattern. The thickness of the film is often on the order of the wavelength of light, which means that the film thickness is much smaller than the separation between the light waves. Thin-film interference is one of many optical interference effects.


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Video Transcript

welcome to our third example video. Looking at thin film interference in this video, we're going to go back to our bubble example where we found that we would need to use the inverse equations because we have one phase shift. Given this and that we have incoming light of 600 30 nanometers. I would like to know how thick does the soap film have to be in order to have constructive interference? Remember, the condition for a construct of interference in this case is going to be equal to M minus one half times Lambda divided by N one where n one. It's going to be our end for the soap, which is 1.5. So in order to find the thickness, all I have to do is move over a T have m minus one half times Lambda over two times and one. If I plug in my lambda and leave em as one, remember, M could be several different industries. 123 and so on. If I said M equals toe one and I plug in 630 nanometers, then I have thickness is equal to 1/4 times 630 times 10 to the negative 9 m, divided by N one, which is 1.5. So we can see here that the thickness would not have to be very thick at all, because we have attend to the negative seven here, divided by some number. So it would be on Lee. A very thin film would be required in order to have this wavelength of light be interfere with itself constructively as it comes reflected off of the bubble.