If $\frac{\text{Path difference}}{\text{Wave length}} = n$ (where $n$ is an integer),what kind of interference is formed?

The ratio of intensities of two waves producing interference is $9: 4$. The ratio of the resultant maximum and minimum intensities will be:

Which optical phenomena can be explained by the wave nature of light?

Consider the following statements about interference of light:
$A$. The interference fringes are equally bright and equally spaced.
$B$. At the centre of a bright fringe,the intensity is four times the intensity of the incident wave.
$C$. For constructive interference of two waves,the crest of one wave coincides with the trough of another wave.
Which of the above statements are correct?

Two coherent sources of intensities $I$ and $4I$ interfere. The maximum and minimum intensities of the resultant wave are:

Two coherent monochromatic light beams of intensities $I$ and $4I$ are superposed. The maximum and minimum possible intensities in the resulting beam are