In a Young's double slit experiment,the source illuminating the slits is changed from blue to violet. The width of the fringes

In Young's double slit experiment, the fringe width is $0.4 \text{ mm}$. What is the distance between $4^{th}$ dark band and $6^{th}$ bright band on the same side of the interference pattern (in $\text{ mm}$)?

In Young's double slit experiment,the amplitudes of the two waves incident on the two slits are $A$ and $2A$. If $I_{0}$ is the maximum intensity,then the intensity at a spot on the screen,where the phase difference between the two interfering waves is $\phi$,is:

In Young's double slit experiment,the $10^{th}$ order maximum is obtained at a point of observation in the interference pattern for a wavelength $\lambda_1 = 7000 \; \mathring{A}$. If the source is replaced by another one of wavelength $\lambda_2 = 5000 \; \mathring{A}$,what will be the order of the maximum at the same point (in $^{th}$)?

Two coherent sources $P$ and $Q$ produce interference at point $A$ on the screen,where a dark band is formed between the $4^{\text{th}}$ and $5^{\text{th}}$ bright band. The wavelength of light used is $6000 \text{ Å}$. The path difference between $PA$ and $QA$ is:

The maximum intensity of fringes in Young's experiment is $I$. If one of the slits is closed,then the intensity at that place becomes $I_o$. Which of the following relations is true?