# Determine the slit-with and slit-distance of a double slit laser diffraction

Parallel laser light with wavelength 633 nm are incident perpendicular against a double slit. 2.50 m behind the double slit is a screen where the pattern can be seen (link below). Determine with the help of the figure the slit-with and slit-distance.

http://s716.photobucket.com/albums/ww168/Pitoraq/?action=view&current=DSC_01821.jpg

Formulas:

Slitwith:

b = slithwith

bSin(v) = λ*m

where Sin(v) ~ v = y/L

b = (λ*L)/(y(diffmin))

Slit-distance:

d = (λ*L)/(y(max))

d = distance

How can i get y(diffmin) and y(max) out of the figure ?(ignore my measurment in the figure) The answer should be b = 0.099 mm and d = 0.30 mm

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TSny
Homework Helper
Gold Member
Hi Firben. The figure shows the combined effect of double slit interference and single slit diffraction. Can you tell us from the figure the locations of the two first-order single-slit diffraction minima and the locations of the two first-order double-slit interference maxima?

This might help: http://en.wikipedia.org/wiki/File:Single_slit_and_double_slit4.jpg

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