Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit)

• A

  $\mathrm{asin\theta }=\frac{\mathrm{\lambda }}{2}$

• B

  $\mathrm{acos\theta }=\frac{3\mathrm{\lambda }}{2}$

• C

  $\mathrm{a} \sin \mathrm{\theta } = \mathrm{\lambda }$

• D

  $\mathrm{a} \sin \mathrm{\theta }=\frac{3\mathrm{\lambda }}{2}$