1. The problem statement, all variables and given/known data I did a physics lab the other day that dealt with two slit diffraction. In my setup, I also saw two faint diffraction minima, and it is my understanding that there is also some single slit diffraction effects. I measured the position a diffraction minimum to be y= 8.775 cm. I am asked to calculate the slit width a using equation sin(theta)=p*lambda/a, where a is slit width. 2. Relevant equations 3. The attempt at a solution My question is do I use a= (p)*lambda/(sin(theta)) or a=(p+.5)*lambda/sin(theta) I know that in single slit diffraction you don't add a .5 to the value for p, but I was just wondering if it is any different for this case.