明纹位置：x = kλD/d
暗纹位置：x = (k+1/2)λD/d
相邻明纹间距：Δx = λD/d
Δx = 0.0011 m
暗纹位置：x = kλD/a
半角宽：θ ≈ λ/a
中央明纹宽度：Δx = 2λD/a
Δx = 0.0022 m