List of top Physics Questions on wave interference asked in Manipal

The path difference between the two waves $y_{1}=a_{1} \sin \left(\omega t-\frac{2 \pi x}{\lambda}\right)$ and $y_{2}=a_{2} \cos \left(\omega t-\frac{2 \pi x}{\lambda}+\phi\right)$ is

The necessary condition for an interference by two sources of light is that