Who was the first to study the phenomenon of interference of light?

In a Young's double-slit experiment,two slits act as coherent sources of waves of equal wavelength $\lambda$ and amplitude $A$. In another experiment,the two slits are arranged to act as incoherent sources of waves of the same amplitude and wavelength. If the intensity at the central point of the screen in the first case is $I_1$ and in the second case is $I_2$,then the ratio $I_1/I_2$ is:

In a Young's double slit experiment with slit separation $0.1\, mm$,one observes a bright fringe at angle $\frac{1}{40}\, rad$ by using light of wavelength $\lambda_1$. When the light of wavelength $\lambda_2$ is used,a bright fringe is seen at the same angle in the same setup. Given that $\lambda_1$ and $\lambda_2$ are in the visible range ($380\, nm$ to $740\, nm$),their values are:

Two identical narrow slits $S_1$ and $S_2$ are illuminated by light of wavelength $\lambda$ from a point source $P$. If,as shown in the diagram,the light is then allowed to fall on a screen,and if $n$ is a positive integer,the condition for destructive interference at $Q$ is that

In Young's double slit experiment,if the wavelength of the light used is doubled and the distance between the two slits is halved,the resultant fringe width becomes $n$ times the initial fringe width. Find the value of $n$.

In Young's double-slit experiment with a source of light of wavelength $6320 \ \mathring{A}$,the first maxima will occur when: