The wavelength of light visible to the human eye is of the order of:

Two monochromatic light waves of amplitudes $3A$ and $2A$ interfering at a point have a phase difference of $60^{\circ}$. The intensity at that point will be proportional to.......$A^2$

Two light sources have amplitudes $a$ and $2a$ respectively. If they interfere with a phase difference of $\pi$,what is the resultant minimum intensity?

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 $I$)

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The phase difference of two light waves changes if they travel through different media having the same thickness,but different indices of refraction.
Reason $R$: The wavelengths of waves are different in different media.
In the light of the above statements,choose the most appropriate answer from the options given below.

$n$ incoherent sources, each emitting beams of intensity $I_0$, are superimposed at a point. The resultant intensity at the point is: