Young's Double Slit Experiment

What happens when you increase distance between slits?

How does the distance from the screen affect the interference pattern?

What is meant by YDSE?

What are Nodal and Anti-nodal Lines in Young's Double slit experiment ?

How do source and image behaves as coherent sources?

How does wavefront division provide coherent sources?

What are coherent sources?

What is intensity division?

Light of $5000 \stackrel{\circ }{\mathrm{A}}$ wavelength is incident on a screen. In diffraction pattern fifth minima is formed at $5 \mathrm{mm}$ from the central maxima if distance between screen and slit is $1 \mathrm{m}$, then width of slit is -  

In Young's double slit experiment ratio of widths of slits is $4:9$, then what is the ratio of intensity of maximum and minima -