If the separation between slits in Young's double slit experiment is reduced to $\frac{1}{3}rd,$ the fringe width becomes $n$ times. The value of $n$ is

In an interference experiment,the spacing between successive maxima or minima is

Consider the following statements in the case of Young's double-slit experiment:
$(1)$ $A$ slit is necessary if we use an ordinary extended source of light.
$(2)$ $A$ slit is not necessary if we use an ordinary but well-collimated beam of light.
$(3)$ $A$ slit is not needed if we use a spatially coherent point source of light.
Which of the above statements is true?

In Young's double slit experiment,if one of the slits is closed fully,then in the interference pattern:

In an interference pattern,the $(n + 4)^{th}$ blue bright fringe and $n^{th}$ red bright fringe are formed at the same spot. If red and blue light have wavelengths of $7800\,\mathring{A}$ and $5200\,\mathring{A}$ respectively,then the value of $n$ is:

In Young’s double slit experiment, how many maxima can be seen on a screen (including the central maxima) if $d = \frac{5\lambda}{2}$ (where $\lambda$ is the wavelength of light and $d$ is the distance between the two slits)?