The light beams of intensities in the ratio of $9: 1$ are allowed to interfere. What will be the ratio of the intensities of maxima and minima?

Two coherent point sources $S_1$ and $S_2$ are separated by a small distance '$d$' as shown. The fringes obtained on the screen will be

$n$ identical waves each of intensity $I_0$ interfere with each other. The ratio of maximum intensities if the interference is $(i)$ coherent and $(ii)$ incoherent is:

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?

If the distance between a point source and a screen is doubled,then the intensity of light on the screen will become:

For the sustained interference of light,the necessary condition is that the two sources should