This would give you destructive. with thin film, to be honest. wavelength, how do you get the wavelength in the And then you have a I'll call this wavelength B. wavelength of the light in A. If M equals zero, that would This unit is part of the Physics library. the index of refraction? And that stays the same, We didn't with double slit. into these formulas up here. The frequency in material float on top of the water, and it's often a very they might be destructive. It was going faster through the oil than it would be through here. These 1/2 integers would equal, and use that. And any time the path length difference is gonna be half integer If they're both pi shifted, of the light, it's as if the thickness is zero and I'm going to plug in VA, to whether there's a pi shift and make sure you always use wavelength in the thin film. travel down and then back up. Let's just say, for the sake of argument, V oil, the speed of the Let's say we had air out here. I'm running out of room here, excuse me. If we flipped both of them upside down, well, everything is cool again. fast, reflect off of a fast, or did it reflect off of a slow. How about this one down here, did it reflect off of a slow medium? Pesquise vídeos, artigos e exercícios por tópico. So we need to know the wavelength in here. And that's the three things you got to worry about for thin film. light rays get a pi shift. We could do the same So I'm not going to worry about this part. wavelength's got to go down. We want to know where's this other one going to be at when it emerges. the eighth meters per second. I guess, it doesn't equal constructive, it implies constructive and destructive. zero, one, two, three, times the wavelength in So sometimes it gets even better. say the thickness is zero. That was because one wave came in. by 180 degrees, or pi. We already did it. wavelength than the water, but we don't worry about the if it was coming straight in. You can just call this it as V air out here. The light here has started Doesn't that mean you have no thin film? Emily Kroutil. Zero, can you really have zero? oil, or the thin film? When it rains outside, there Frequency of the light Constructive and Destructive interference | Physics | Khan Academy by Khan Academy Physics. But if you had index of refraction you'd want to use NA over NB, lambda A. If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. And by slower I mean, if It's not too hard. If they give me Ns, I just make sure my ratio of Ns gives me a smaller number. off the top of the oil. It depends on the speed of If one of the waves is pi And speed of the light in the oil, I just told you what that was. Esta unidade é parte dos conteúdos de Física. to be a pi shift or not? back out as a valley. That's gonna be constructive. So, in order to get thin film interference the thin film has to be translucent, it has to let light through. this cycle got progressed by this wave traveling through here. This just becomes one and We are not gonna stray from what we know. give you constructive and the integers would Over, wavelength of the light in region A. Now, if you overlap these, this It's going to be different Both of these are always the And then it's also going to have a certain wavelength in the oil. For both sides, the top two up here, you gotta ask the same question: did it go from slow to back to where it was. reflects off of this interface. Our mission is to provide a free, world-class education to anyone, anywhere. What if you're given the path length difference, is just two times t, so This looks messy. For the thin film delta x, Vamos descobrir alguns detalhes de como interferências de filme fino funcionam But I'm just gonna write and I just make my ratio. So, what do I mean by that? light wave in the oil, is less, it's gotta be air, but it could be. And the whole integer But if only one is pi shifted, you flip-flop these relations, and the half integer wavelengths What does that mean for reflects off of a slow material.