The contrast in the fringes in an interference pattern depends on

Two waves of intensity ratio $1:9$ cross each other at a point. The resultant intensities at the point are $I_1$ when the waves are incoherent and $I_2$ when the waves are coherent with a phase difference of $60^{\circ}$. If $\frac{I_1}{I_2} = \frac{10}{x}$,then $x = . . . . . . . . . . .$

The colour of light is characterised by which of the following characteristics?

In an interference pattern,two waves of intensities $I$ and $4I$ are used. At point $A$,the phase difference is $\frac{\pi}{2}$,and at point $B$,the phase difference is $\pi$. The difference in intensities at points $A$ and $B$ is: (in $I$)

Two coherent sources of intensity ratio $9:4$ produce interference. The intensity ratio of maxima and minima of the interference pattern is

$A$ ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness $t$ and refractive index $n$ is introduced in its path,then the optical path