What is Young's interference? (b) How should the number of observable interference fringes change as the distance between the two slits increases? Assume that the slit width remains unchanged. (c) How should the number of observable interference fringes change as the slit width decreases? Assume that the slit separation remains unchanged. (d) What is a missing fringe?

b) increase.

c) decrease.

d) Fringe is said to be a missing fringe when interference maxima overlap with diffraction minima.

Explanation:

a) Young's interference is the interference phenomenon related to the light waves. Interference is the superposition of light waves. It proved the wave nature of light. Interference can be either constructive or destructive.

b) If the distance between the two slits increases, the number of fringes also increases. d sinθ = m λ. Here d is the slit width and m is the order of fringes. It shows that as d increases, m also increases.

c) Similarly, as d decreases, number of fringes decrease.

d) Fringe is said to be a missing fringe when interference maxima overlap with diffraction minima.