College Help

:You are welcome. Actually I think you should have sent a PM to bd popeye and his daughter would give you the answer right away:nana:

szbd said:

:You are welcome. Actually I think you should have sent a PM to bd popeye and his daughter would give you the answer right away:nana:

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Thanks..But she's a Spanish Major..I think ...Since I live in Iowa and she lives in San Diego I have no idea what level of math she takes...But I garuntee you her grade is an A+

A question relating to stealth aircrafts. Just want to clarify my answer if its correct and to see if your answers are the same as mine:
Question: A possible means for making an airplane invisible to radar is to coat the plane with an antireflective polymer. If radar waves have a length of 2.10cm and index of refraction of the polymer is n=1.7, how thick would you make the coating?
Working out: Thickness= 0.021m/(2x1.7)
=0.00618m Damn sure this is the answer but want to clarify it with you guys before submitting.

This question however is a level more difficult in which I'm not to confident that it is correct for submission:
Question: Young's double-slit experiment is performed with 529nm light and a slits-to-screen of 1.7m. The eleventh interference minimum is observed 7.34mm from the central maximum. Determine the spacing of the slits.
Working: (1.7/0.00734) x 11 x (5.29x10^-7)
=0.00135

Need help with this question people. I would ask my lecturer for help but I cant understand his english properly. Confuses me more sometimes. haha

The first one i think you got it wrong. You need a half wave length back to counter the original wave. The wave goes in then out, so the thickness should be half of a half wave length, in stead of a half wave length.

let me see the second one.

OK, the second one.

So if it's as simple as I think. The equation is X=(L/d)r. Where X is the distance between lines after interference, L is the distance between slits and wall, d is the distance between slits and r is the wave length.

You have X, L and r now, so d=Lr/X

you have L=1.7m and r=529nm. You have the distance of the 11th dark line to the 0th bright line, that's 7.34mm. So that means 10.5X=7.34, instead of 11. Because you have a 0.5X from 0th bight line to the 1st dark line.

szbd said:

The first one i think you got it wrong. You need a half wave length back to counter the original wave. The wave goes in then out, so the thickness should be half of a half wave length, in stead of a half wave length.

let me see the second one.

OK, the second one.

So if it's as simple as I think. The equation is X=(L/d)r. Where X is the distance between lines after interference, L is the distance between slits and wall, d is the distance between slits and r is the wave length.

You have X, L and r now, so d=Lr/X

you have L=1.7m and r=529nm. You have the distance of the 11th dark line to the 0th bright line, that's 7.34mm. So that means 10.5X=7.34, instead of 11. Because you have a 0.5X from 0th bight line to the 1st dark line.

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Thanks alot for the help on the 2nd question: yeah i had to convert the 7.34mm to 0.00734m cause we've got to follow the MKS rule. With the stealth question I had submitted it and have got it correct. Cause there is no need to half the wavelength cause its the radars hitting the plane and so it the radar signature doesnt reflect or other words bounce off. It absorbs the radar signature so its turns out to be 0 in the end. But thanks for the help anyway. by the way it sounds like your either an engineer or physics person, curious what is your proffesion? cause mines engineering.

I'm an EE engineer. But the answer to your questions all came from my high school memory.

szbd said:

I'm an EE engineer. But the answer to your questions all came from my high school memory.

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hey szbd, how is life being an EE engineering? i am currently an EE student in college and i wonder if its a field of work that people can really enjoy?

kunmingren said:

hey szbd, how is life being an EE engineering? i am currently an EE student in college and i wonder if its a field of work that people can really enjoy?

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EE engineering is a very big area. I think currently the most positions are working with computers, not with those big machines. The common type of work, I think, is make a small package work. This package can be software or hard ware. The software can be a relatively independent thing, like developed from ANSI C, or developed from some existing specialized tools. The hardware can be design a chip, design a board, or put your algorithm in to a chip or a board.

The key is familiar with standards, protocals, drivers, etc. How everything communicates with each other is the most important thing to learn. How the data is transfered from a CPU to a periperal, then to memory, then to another CPU......

To implement the functions, formulas in the books is very simple. To develop your own algorithm and implement is not hard either. The hard part is the communication, move data from here to there, read from this address, write to that address, mapping address, etc. Because as an EE engineer, we always work with things much much dummier than PCs.

Or, use those specialized tools to develop softwares or perform simulations. I'm not in that kind of area though, my wife is. It also demands a lot of experience.

Team work is very important too, and it's very complicated to describe. But one thing i'd like to point out is, be patient with block diagrams. It's very important work to read and to draw those diagrams. Young people usually think that's tedious or just some kind of show bussiness. But in fact it's not.

About the life of an EE engineer, I think it's peaceful overall. As an EE engineer, usually you get fair payment, regular working time, comfortable working environment with AC etc, and no danger. No strict time line usually.

At the beginning, if you do not have high degree or extraordinary skills, they will give you really tedious work. You feel you know nothing, because they work on sth you never saw (this is the usual case, can be some exceptions of course). You will have some pressure, frustration, but you will be fine after 1 year or so. If you have high degree, that's a different story. They may get you to do some R&D work with more theory stuff involved.

thanks for the help, i think i might end up working with computer hardware too, since there are a lot of oppurtunity there. Btw, which university did u attend for you EE degree?

I've been to PKU, HKUST and currently doing part time PhD in waseda university, japan.