If I decrease the slit distance the pattern on the screen would spread out.
The two slits are separated from the screen by an integer number of wavelengths plus one-half wavelength. Peak and trough converge. The wavelength can be determined from the fringe spacing if this Fraunhofer interference pattern is displayed on a screen L distance from the slits.
The space between two consecutive bright spots (maximas, when constructive interference occurs), or two consecutive dark patches, is known as the fringe width (minimal, where destructive interference takes place).
fringe width = λ L / D
where λ is the wavelength of light used, L is the distance of the wall from the source of light, and D is the slit distance. If we increase λ, fringe width will increase, and therefore pattern will spread out.
To know more about fringe width refer to: https://brainly.com/question/14438105
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