1. The problem statement, all variables and given/known data http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s02_qp_2.pdf question no. 7b 2. Relevant equations dsin∅=nλ 3. The attempt at a solution I subtracted the two angles and got 26 degrees. So then I plugged it all into the equation: dsin26=2 X 630x10^-9. My answer is half the actual answer because the angle the answer sheet has is 13 degree. Why do they take it as 13 degree??