What are coherent sources ?

What are incoherent sources?

In Young's double slit experiment, the two slits act as coherent sources of equal amplitude 'a' and of wavelength lambda . In another experiment with the same setup the two slits are sources of equal amplitude 'a' and wavelength lambda but are incoherent. The ratio of intensities of light at the mid point of the screen in the first case to that in the second case is ....

In Young's double slit experiment, the two slits act as coherent sources of waves of equal amplitude A and wavelength lambda . In another experiment with the same arrangement the two slits are made to act as incoherent sources of wave of same amplitude and wavelength. If the intensity at the middle point of the screen in the first case is l, and in the second case is I_(2) then the ratio (I_(1))/(I_(2)) is .......

Explain the intensity of the point of superposition of the waves emanating from it by explaining the coherent and incoherent sources.

If the path difference of the point on the screen from a coherent source is constant, what is shape of trajectory of the point on the screen ?

Which out of following cannot produce two coherent sources ?

The resultant amplitude in interference with two coherent sources depends upon-

Assertion (A) : No interfrence pattern is detected when two coherent sources are very closer to each other. (i.e separation almost zero) Reason (R ) : The fringe width is inversely proportional to the distance between the two slits