Question

Double Slit interaction

Run 1:

Wavelength = 400nm; Slit Width = 1600nm; Slit Spacing = 3500nm

Run 2:

Wavelength = 400nm; Slit Width = 1600nm; Slit Spacing = 5000nm

Run 3:

Wavelength = 500nm; Slit Width = 1600nm; Slit Spacing = 3500nm

Run 4:

Wavelength = 500nm; Slit Width = 1600nm; Slit Spacing = 5000nm

Run 5:

Wavelength = 600nm; Slit Width = 1600nm; Slit Spacing = 3500nm

Run 6:

Wavelength = 600nm; Slit Width = 1600nm; Slit Spacing = 5000nm

What is the reason that an interference pattern is observed in each run?

What happens to the interference pattern when the slit spacing increases but wavelength is not changed?

What happens to the interference patter when wavelength is increased but slit spacing is not changed?

Answer 1

in each run , waves from two slits mix with each other at the screen placed at some distance from the slits . the trough of one wave falls on trough of other and we get a bright spot or maxima at the screen . and when trough of one wave falls on crest of other, we get a dark spot at the screen .

position of fringes on the screen is propotional to wavelength and screen distance . also position of fringes on the screen is inversly propotional to slit width "d"

when slit spacing increases , width of fringes becomes narrower

when wavelength is increased , the fringe width becomes wider as fringe width is directly propotional to wavelength

Y = n D