If the angle of incidence of $X$-ray of wavelength $3 A$ which produces a second order diffracted beam from the (100) planes in a simple cubic lattice with interlayer spacing $a=6 Å$ is $30^{\circ}$, the angle of incidence that produ ces a first-order diffracted beam from the (200) planes is

• A

  $15^{\circ}$
• B

  $45^{\circ}$
• Correct answer
  C

  $30^{\circ}$
• D

  $60^{\circ}$

Hence, the correct answer is option: 'C'.