For constructive interference to take place between two monochromatic light waves of wavelength $\mathrm{\lambda }$, the path difference should be

• A

  $(2\mathrm{n}-1)\frac{\mathrm{\lambda }}{4}$

• B

  $(2\mathrm{n}-1)\frac{\mathrm{\lambda }}{2}$

• C

  $\mathrm{n\lambda }$

• D

  $(2\mathrm{n}+1)\frac{\mathrm{\lambda }}{2}$