Physics help!!

[qwerty04]

hey guys
As a lot of you may know, the umat was last week and on the same day we were meant to do a major physics prac.....
So, i now have this massive physics prac report to complete in less than 3 days and have no idea where to begin....and was wondering if anyone who has done well in  physics could help me out? 

The prac is about Young's double slit experiment and comparing the double slit results with diffraction grating etc..

Anyone who is willing to help, please message me
thanks

[PB]

Uh yeah sure m9,
whats up? will try my best to help you

[qwerty04]

Ok thanks

So the aim was to investigate the interference of light using two methods and find the wavelength of the light. (Source of light was sodium lamp). First was using an interferometer with the single slit and double slit etc. Second was using the diffraction grating and spectrometer.

Btw i missed out on the theories because of umat.

Some of the questions im stuck on...
 - If the slit spacing was not given how could you determine the wavelength? What measurements and or calculation would be required?

- Which method is likely to  give a more accurate value? Which method is likely to give a more precise value?

- If a source of monochromatic blue light were used in place of the sodium lamp, how would this change the results? Include in your answer how it would change the accuracy and precision of the results?

[qwerty04]

I could send pictures of procedure and results etc..
but this thing has a limit of 1mb
the smallest pic is about 2 mb

i could email them to you ?
if you can pm me the email address?

[PB]

Some of the questions im stuck on...
 - If the slit spacing was not given how could you determine the wavelength? What measurements and or calculation would be required?

- Which method is likely to  give a more accurate value? Which method is likely to give a more precise value?

- If a source of monochromatic blue light were used in place of the sodium lamp, how would this change the results? Include in your answer how it would change the accuracy and precision of the results?

1. Have you seen this formula path diff=nw  (where w is wavelength)  before? It should be in your textbook. n is 0,1,2,3...etc. where 0 is the central fringe (brightest one), 1 is the next brightest one and so on. Basically you choose one bright fringe, and measure the distances between that fringe and each of the two slits. One distance would be slightly longer obviously. The difference in those two distances is the path difference.  Sub that into the pd=nw formula, and using the correct n it will leave you with the only variable left to be equated - the wavelength.


2. Not really sure but I think the above method is more accurate because you only have to measure two distances. Whereas if you were finding the values for the x=wL/d formula, you have to measure x,l and d to get w  (three things) so more room for human and instrumental error.

3. All I know is that blue light has a smaller wavelength than sodium/yellow light so obviously that changes your results in that, you will get a smaller wavelength value. As for the accuracy bit (this is a bit of a speculation), because blue wavelength is smaller, fringe spacing would decrease which would lead me to think that the measurements would start to lose accuracy. Because as you may know, accuracy is harder to attain in instruments when the values start getting smaller and smaller.  You need to buy more and more expensive equiptment to measure smaller quantities with accuracy.

[PB]

I wish you all the best with your prac and am sorry to hear about the inadequacy of your teacher. that truly sucks, but its no indicator of you ability to succeed!
And because you missed out on learning the theory, I highly recommend you take the time to hit the textbooks, youtube, Vtextbook (been hearing good things from them...)  or whatever on earth helps you understand the concepts... before heading into the SAC.