# Search results

1. ### Converging Lasers of Different Wavelengths

-UltrafastPED Thanks for that info. I'm starting to do Optics for my research and I'm slowly getting my feet wet. The "dogleg" setup will hugely help me. The idea is so simple, but effective. I don't know about cutting the lens in half, my adviser might kill me, but I'll give your other...
2. ### Converging Lasers of Different Wavelengths

I hope this is the right place to ask this. It is an experiment question. I have a 785 nm laser and a 1550 nm laser and I need to converge them down to a point. Now I could just manually align the lasers on the same XY-plane and have them hit that spot, but for reasons I don't want to...
3. ### How to go about solving this first-order nonlinear differential equation?

Thanks a lot! That made the problem a lot simpler. I can't believe I didn't carry that \eta over.
4. ### How to go about solving this first-order nonlinear differential equation?

I saw this post at stackexchange: I ran across this post when trying to solve a homework problem. But I have no idea how he got that solution for that. When I use the Euler-Lagrange, I get this diff eq below. Here is the simplest form I have managed to get it in...
5. ### Tips on writing the Lagrangian

Thanks. I'll just try to do as much problems with different scenarios as I can. And I'll keep your tip in mind.
6. ### Tips on writing the Lagrangian

^ Yeah sorry, that is what I meant. That hint helped me thanks. It is like watching a magic trick. Once you know the trick, it becomes simple. Haha. So do you have any tips in general on how to better this "intuition"...? Or is it just about gaining more confidence...?
7. ### Tips on writing the Lagrangian

Hey guys. I'm trying to gather some tips that people have acquired that helps them write the Lagrangian for a system. Obviously, the classic examples are drilled into our heads over and over, but just when you think you can tackle any problem the professor throws at you, there is that tricky one...
8. ### Derivation of Potential Energy for two masses attached to three springs

Ahh... That was my gap in my understanding. I don't know why I didn't see it that way from the beginning. With that in mind, I derived the right potential. Thank you guys for helping! :smile:
9. ### Derivation of Potential Energy for two masses attached to three springs

Hmm... I see what you mean. Let me look into that in the morning. It is about 2:15 in the morning for me and I got to get some shut eye. From a quick glance, I would argue that I never wrote down my forces in "x_2-x_1" terms, so I would not run into that. But I'm sleep deprived so I may not...
10. ### Derivation of Potential Energy for two masses attached to three springs

^ Yes you are right. I just typed it wrong when I was reading it off of Taylor. Thanks For the integration, yes I made it really general and simplified, but it is right. I'm still integrating along the general x-axis since both variables, though they are named different, still vary in the...
11. ### Derivation of Potential Energy for two masses attached to three springs

First of all, my question isn't completely unrelated to a homework question. I know how to answer that question using definitions in the book and mechanically get to the end. But I wanted to start from basic principles and arrive at the same answer. This lead to a contradiction which sent me on...
12. ### Quick help needed on a Matrix Multiplication

-chogg Yes. That helps. I'm using Matlab and remember seeing a code in the User's Guide that probably does the same thing. Thanks. :tongue2:
13. ### Quick help needed on a Matrix Multiplication

Okay, after experimenting with your post, micromass, I found out it does work for any value you want to pick off. So I want to thank you for that. But I have to translate this into coding and it seems like it is going to be more code to write this than just my original idea to use an if and else...
14. ### Quick help needed on a Matrix Multiplication

-micromass Yes, that seems to work. But really what I need is what chogg stated. I need to able to "mask out", as chogg perfectly put it, more than one element. Will that work for picking out more than one element..? Thanks for the help. -chogg Yes, that is exactly what I need to do. You see...
15. ### Quick help needed on a Matrix Multiplication

I have a small problem where I remember I learned it in the past. But now I can't seem to recall how to do it. I searched on google, but I think even though it is probably really easy, I may not have worded it right to get the references I want. So I decided to ask here. Here is the problem...
16. ### A Geometry problem that is giving me trouble

Yep, that does it! :cool: Thanks so much! This is going to help me out a lot. I wish I could give you something. So here are some http://freeinternetcookies.com/" [Broken]. You have to click yes. :smile:
17. ### A Geometry problem that is giving me trouble

Well first of all, thank you for replying. I followed your steps and it makes sense. I was a bit uneasy in understanding the normalizing parts, but I trusted you. (It is definitely because of my limited knowledge than yours. :shy:) So I decided to use your end result and I solved for a using...
18. ### A Geometry problem that is giving me trouble

So here is a picture I quickly made in photoshop that has the problem: [PLAIN]http://img21.imageshack.us/img21/9406/trigproblem.png [Broken] The rectangle's dimensions are known. (w & h) So it follows that the angle, "@", and the diagonal, "d", is also known. The width between the two...
19. ### Question about length contraction (geometric way)

Okay, I see what we did wrong. So basically there would be no way to get length information with just pure geometry on a piece of paper... We are forced to use the derived formulas..? (L'=L*sqrt(1-v^2) , t'=...) Thanks for everything. I'm probably going to post more throughout this semester...
20. ### Question about length contraction (geometric way)

:smile: I have already come across it in my Modern Physics last year. And of course you are not becoming a bore. I think I see what you are talking about. The original L(0) that is shifted up in my figure in the x'-x'L ...? If that is the case, then you should know that the horizontal L(0)...
21. ### Question about length contraction (geometric way)

Yes, I was wondering what that was about. :) But I edited my last post with more details on how we approached it.
22. ### Question about length contraction (geometric way)

@Mentz and Jesse I think I see where you guys are coming from. But the diagram that I posted may be misleading. The L(0) that touches the t' and t'L is just there to show the magnitude of L(0). Not that it shows any movement. The L' that touches x' and x'L axis is the one that from the x-t...
23. ### Question about length contraction (geometric way)

I'm doing some independent study with a professor at my university. He has taken one GR class and he said that it was not a good experience. So we are in a sense learning together as we pursue this. We are using the book "A First Course in General Relativity" by Schultz. We are doing problem...
24. ### Hall Effect Probe/Sample Mount (Design)

I'm sorry I should have said Hall voltage measurement. We will know the value of the B-field and will be solving for the sheet carrier density. Our magnet range is around .5-1.5 Tesla. Most of our work will probably be around .5-1 Tesla. The outline we are following is here...
25. ### Hall Effect Probe/Sample Mount (Design)

Me and a friend are working on a research project that involves four-point electrical measurements. (Van der pauw) To do a hall effect measurement, the sample and probes have to have a strong magnetic field pass through. So we want some design ideas on constructing the mount that will have to be...
26. ### X-ray Fluorescence angle question.

^ Thanks for that. Sorry for the late reply. I was really busy this weekend. I'll ask him about it today and will get back to you. I'm pretty sure he told me that he was doing X-Ray Fluorescence. I'm sure he knows about the basic laws of reflection. I think the question was more what angle is...
27. ### X-ray Fluorescence angle question.

First of all, I'm not the one doing this experiment. I've just finished my first year in college and I'm sort of just helping all the upper-level with their research and whatnot. So my knowledge is very limited. With that being said, one of those student is doing X-ray Fluorescence. He was...