## anonymous one year ago When does the double-slit interference have its first dark spot on either side of the central peak intensity? **will draw image!** A. when the paths d_1 and d_2 differ by one wavelength B. when the paths d_1 and d_2 differ by half a wavelength C. when the waves arrive in step, or "in phase" with each other D. when the paths d_1 and d_2 have the same length

1. anonymous

|dw:1433263092745:dw|

2. anonymous

|dw:1433263217576:dw|

3. anonymous

and then the other parts are different shades of light!

4. anonymous

the parts shaded in black are the darkest areas and the rest are lighter, but different shades of light if that makes sense haha :P

5. Michele_Laino

ok!

6. Michele_Laino

we have these two conditions: $\begin{gathered} {\text{path difference = n\lambda }}{\text{,}}\quad {\text{bright regions}} \hfill \\ {\text{path difference = }}\left( {{\text{n + }}\frac{{\text{1}}}{{\text{2}}}} \right){\text{\lambda }}{\text{,}}\quad {\text{dark regions}} \hfill \\ \end{gathered}$

7. Michele_Laino

$\begin{gathered} {\text{path difference = }}n\lambda ,\quad {\text{bright regions}} \hfill \\ {\text{path difference = }}\left( {n + \frac{1}{2}} \right)\lambda {\text{,}}\quad {\text{dark regions}} \hfill \\ \end{gathered}$

8. anonymous

ok! what happens next?

9. Michele_Laino

where n is an integer, namely n=0, +/-1, +/-2,...

10. Michele_Laino

$n = 0, \pm 1, \pm 2,...$

11. Michele_Laino

the first dark region is given setting n=0

12. anonymous

ohh ok!what does that mean?

13. Michele_Laino

It means option B

14. anonymous

ohhh okay i see now :) cool!! thank you1!:D

15. Michele_Laino

:)