Best lecture series I have ever gone through in youtube - concise and to the point.

@jacobvandijk6525

3 жыл бұрын

Let's say, one of the best series. I guess you (and I) haven't seen them all.

Wow!! Great presentation. I have been dealing with optics for many years. This is one of the best KZread lectures I have ever seen. Well-presented and very clear.

Hi Sander, First thanks so much for these videos. I've got no college math background, having taught myself a handful of pieces across a range of math topics, but still feeling like I'm missing huge amounts, so finding your videos that are clear, concise, and with enough context included that I'm able to understand reasonably is fantastic. As far as feedback you've received that you're going too fast, I wouldn't trade off being succinct, it's video - we can pause and replay all we need to achieve understanding. Anyway, my question, at 7:21 you talk about the destructive interference of other path lengths. For incoherent light does this still work because for any given phase there'll be other photons sharing that phase to destructively interfere at those points? i.e. you can treat it as coherent because the incoherent light could just be viewed as integrating over all sets of coherent light, each of which destructively interferes? (P.S. if you have any tips for learning mathematics, I'd welcome them; the hardest part seems to be figuring out the order as there's interconnectedness in these concepts, it's not like there's an obvious linear path through, and it's not like I've even seen a DAG of all the branches/concepts to try infer or build a path through with)

@SanderKonijnenberg

3 жыл бұрын

Hi Alan, thanks for the kind remarks. Regarding your question: classically speaking (so without making reference to photons), incoherence occurs because of uncorrelated random phase fluctuations at different field points. In that case, one cannot define a phase difference between those points, and therefore the fields they produce cannot interfere (I have another video on coherence). However, at 7:21 I consider a field from a single quasi-monochromatic point source. That field is always coherent with itself as it propagates, so it can interfere with itself. About learning mathematics: I'm not sure what your current level is and what your goal is, but have you checked KhanAcademy www.khanacademy.org/math ? There they have a broad set of topics presented in a rather structured manner. For learning optics I would say: complex numbers (complex exponentials are commonly used to describe waves), partial differential equations (the wave equation is one), Fourier transforms (basically for adding and decomposing into plane waves). Vector calculus is useful once you start working with the electromagnetic nature of light (electric and magnetic fields are vector fields, Maxwell's equations are vectorial partial differential equations). Linear algebra (matrices, eigenvectors/eigenvalues) tends to be useful in general, but absolutely essential for quantum mechanics.

@skyphyr

3 жыл бұрын

@@SanderKonijnenberg Thank you very much. I've actually watched almost everything in this playlist now (I'm currently on the last one - just I've been slow as I try understand each step). I understood that you were talking about coherent light in the video, but these properties for reflection etc have been using in the geometric optics and, I assume, work equally for incoherent light. This made me curious given you explicitly cited the coherence and interference how it would explain them also applying to incoherent light. My goals with math are really just to arm myself with more tools for problem solving. I've gone through Strang's Linear Algebra course that's available online and done most of the "Mooculus" calculus course. Really appreciate your calling out particular areas as that will help focus where I need to go first for this material.

@SanderKonijnenberg

3 жыл бұрын

@@skyphyr Ok, I think I understand the question. What I'm trying to do here is demonstrating how the ray picture (incoherent limit) arises from the wave (rays+phase) picture. So I wouldn't say 'the argument also applies to the incoherent case', rather 'the incoherent case follows from the coherent case via this argument' (when we assume the wavelength is very small compared to the scale at which we make observations). To give an analogy, it would make sense to argue how classical physics can be derived from quantum physics in a certain limit, but it wouldn't make sense to apply quantum physics to a completely classical system. I hope that made some sense. Good luck with your studies!

@skyphyr

3 жыл бұрын

@@SanderKonijnenberg thanks, that explanation helps understand how the incoherent case follows. Looking forward to getting to the Wigner Distribution (the reference to which I'm Goodman's book) first lead me to your videos. So glad you had everything before to give me a shot at understanding it when I get there. :) Thanks again for the videos and your time in replying to my questions.