rtareen
- 162
- 32
Instead of talking about the simple of case of reflection interference due to a single film, this book starts off with two films with an angled air wedge between them. They talk about the "thickness", ##t##, of the wedge, but this thickness varies along the length of the films (Figure 35.`12). This is and something else is causing me confusion when it comes to the example problems at the end.
Firstly, all of this is impossible because the book itself says that we are restricting discussion to normal incident rays. But you can see in figure 35.12 that the incident ray from the air wedge approaching the second glass film is not normal. Is this all just an approximation? How is it justified? I don't see how you can introduce this angled air wedge problem when you just proclaimed that all incident rays must be normal to the interfaces.
Second, in example problem 35.4, we use the equation ##2t = m\lambda## to try and find the positions along the length where there will be destructive reflection. But the problem is that the thickness of the air wedge is changing with each position, yet we use the same equation ##x = m(1.25 mm)## for each position when the thickness is changing with position. Or does the thickness depend on which value of ##m## you choose? That would make sense.
Finally, the book doesn't really say it, but when we talk about the equation ##2t = m\lambda##, both ##t## and ##\lambda## are characteristics of the second material only right? Thats what I think. Because were looking at how many wavelengths the ray travels through the thickess of the second material twice, right? The book doesn't say this clearly, and I want to confirm if this is right.
Firstly, all of this is impossible because the book itself says that we are restricting discussion to normal incident rays. But you can see in figure 35.12 that the incident ray from the air wedge approaching the second glass film is not normal. Is this all just an approximation? How is it justified? I don't see how you can introduce this angled air wedge problem when you just proclaimed that all incident rays must be normal to the interfaces.
Second, in example problem 35.4, we use the equation ##2t = m\lambda## to try and find the positions along the length where there will be destructive reflection. But the problem is that the thickness of the air wedge is changing with each position, yet we use the same equation ##x = m(1.25 mm)## for each position when the thickness is changing with position. Or does the thickness depend on which value of ##m## you choose? That would make sense.
Finally, the book doesn't really say it, but when we talk about the equation ##2t = m\lambda##, both ##t## and ##\lambda## are characteristics of the second material only right? Thats what I think. Because were looking at how many wavelengths the ray travels through the thickess of the second material twice, right? The book doesn't say this clearly, and I want to confirm if this is right.