Suppose you added to the single slit an identical slit a distance d=0.25mm away
from the first. draw the resulting interference pattern you might expect on the same
screen. what happens when we increase the distance between slits ? what
happens in the limit that d becomes arbitrarily large?

a) See attachment

b) The pattern converges towards central order

c) Very bright spot at central order and rest is dark and contrast of pattern increases.

Explanation:

b) According to Young's Double slit experiment the following relationship is given:

where,

λ = wavelength of light used (m)

x = distance from central fringe (m)

d = distance between the slits (m)

n = the order of the fringe

L = length from the screen with slits to the viewing screen (m)

Using the formula if we increase the (d) i.e distance between slits we see that (x) distance between fringes decreases and the patterns of bright and dark spots is alternating more frequently.

c) When d is arbitrarily large the x is arbitrarily small.

Hence, the entire pattern converges on to the film in a small space with millions spots of bright and dark spots alternating together to forma big bright spot and contrast of pattern increases.

increase masses, decrease separation

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