Consider light from a helium - neon laser ( = 6 3 2 . 8 nanometers )

Consider light from a helium$-$neon laser $(\lambda =632\mathrm{.}8$ nanometers$)$ striking a pinhole with a diameter of $0\mathrm{.}390mm.$

At what angle θ ${}_1$ to the normal would the first dark ring be observed?

Express your answer in degrees, to three significant figures.