Find the angle of diffraction (in degrees) for first secondary maximum of the pattern due to diffraction at a single slit. The width of the slit and…

$\displaystyle \theta=(2 n+1) \frac{\lambda}{2 a}$ For first secondary maximum $\displaystyle n=1$: $\displaystyle \theta=\frac{3 \lambda}{2 a}$ $\displaystyle \theta=\frac{3 \times 550 \times 10^{-9}}{2 \times 0.55 \times 10^{-3}}$ $\displaystyle \theta=1.5 \times 10^{-3}$ radian $\displaystyle =0.086$ degree