The two coherent sources of equal intensity produce a maximum intensity of $100$ units at a point. If the intensity of one of the sources is reduced by $36\%$ by reducing its width,then the intensity of light at the same point will be:

Two coherent sources $S_1$ and $S_2$ are separated by a distance four times the wavelength $\lambda$ of the source. The sources lie along the $y$-axis,whereas a detector moves along the $+x$-axis. Leaving the origin and far-off points,the number of points where maxima are observed is

An interference pattern is observed at $P$ due to the superimposition of two rays coming from a source $S$ as shown in the figure. The value of $l$ for which maxima is obtained at $P$ is: ($R$ is a perfectly reflecting surface)

If the wavelength of light is $4000 \, Å$, then the number of waves in a length of $1 \, mm$ will be:

Interference fringes are produced on the screen by using two light sources of intensities $I$ and $9I$. The phase difference between the beams is $\pi / 2$ at point $P$ and $\pi$ at point $Q$ on the screen. The difference between the resultant intensities at points $P$ and $Q$ is $(\cos 90^{\circ}=0, \cos 180^{\circ}=-1)$. (in $I$)

Two beams of light having intensities $I$ and $4I$ interfere to produce a fringe pattern on a screen. The phase difference between the two beams are $\pi/2$ and $\pi/3$ at points $A$ and $B$ respectively. The difference between the resultant intensities at the two points is $xI$. The value of $x$ will be.