In a Fraunhoffer diffraction experiment at a single slit using light of wavelength $400 \mathrm{nm}$ , the first minimum is formed at an angle of $30°$ . Then the direction $\theta$ of the first secondary maximum is

• A

  ${\mathit{tan}}^{-1}\left(\frac{4}{3}\right)$
• B

  ${60}^o$
• Correct answer
  C

  ${\mathit{sin}}^{-1}\left(\frac{3}{4}\right)$
• D

  ${\mathit{tan}}^{-1}\left(\frac{3}{4}\right)$

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