In young’s double slit experiment with a source of light of wavelength 6320 Å, the first maxima will occur when  

• A

  $\text{ Path difference is }9480\text{Å}$

• B

  $\mathrm{Phase} \mathrm{difference} \mathrm{is} 2\mathrm{\pi }/3 \mathrm{radian}$

• C

  $\text{ Path difference is }6320\text{Å}$

• D

  $\text{ Phase difference is }\mathrm{\pi }\text{ radian }$