I have posted this question some time ago but it was only upon registration, and that it only allows up to 500 characters in Project Questions. This time, here's the complete one:

The following questions are about an experiment where laser pointer can be used to determine the d (data track spacing) of CDs:

1. Is it possible to have a negative angle for θi ? If so, when does this happen?

2. What if the reflected ray isn't equal to θi ? Shall the reflected ray be ordered m=1 automatically ??

3. θi is placed to the right of the normal and there is a diffracted ray to the right of θi. What should this diffracted ray's order be ?? And the angle... is it positive or negative ??

4. What if the computed d is negative ?? Is this reasonable or absurd ?? Or is there something wrong with substitution of values, especially the signs ??

5. What if the averaged d-values for some order of diffraction column is negative ?? Is this an error ?? What does this mean ?

6. Since it is mentioned that the d computed using the formula d=mλ/(sinθm-sinθi) is in nm when λ is in nm, how is the computed value used in determining data track spacing ?? Is it that when d is large, then the CD has low storage capacity or the other way around ??

How shall the computed d-values determine storage capacity of CD ??

7. In my thesis' Review of Related Literature, there's a part that says, "On a CD, the space between tracks is about 1.6 microns versus spacing on a DVD-R which is about 0.74-0.8 microns."

If so, how can nm be converted to microns ? Is it possible ?

8. Can nm be converted to MB to see if the storage capacity label of a CD matches with the computed ones ? If so, how ?

9. Lastly, how is the d=mλ/(sinθm-sinθi) formula derived ?? What is the relationship of each variable to each other ?? What are the principles supporting this formula ??

Much help shall be appreciated. My paper is due on September 20, 2011 and the defending for my project is on Sept. 21, 2011 yet I am uncertain with what I am doing to the experiment. For your reply kindly do so in my email address which I entered upon registration.