for nth dark fringe, this difference nth b fringe and nth dark fringe this is the path difference will be lambda by 2. we will get nth b fringe if this is the path difference and n plus 1 dark fringe for this n equal to n plus 1 if we put this will be the path difference.
ஆவது பட்டை = Xn+1 d/ D = λ/2. பாதை வேறுபாடு இவ்வாறாக இருக்கும் , எனில்