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# Re: [Phys-L] Lower limit for a slit width?

The complete answer depends also on number of slits. As Carl Mungan says quite correctly, we do not see much of a diffraction pattern with a very narrow single slit, because there are no minima on the screen in this case. However, already with 2 such slits we can observe diffraction minima, provided the separation between the slits exceeds the half-wavelength. In this case not only the slit width, but also the distance between the neighboring slits matters.

Moses Fayngold,
NJIT

On Tuesday, May 13, 2014 12:27 PM, Carl Mungan <mungan@usna.edu> wrote:

is there a lower limit for a slit width, say, in terms of
wavelenght for seeing a diffraction pattern?

If the slit width a is smaller than the wavelength lambda, then you
don't really see much of a diffraction pattern, because there are no
minima on the screen. So all you see is a portion of the central
maximum:

sin(theta)=m*lambda/a exceeds 1 for any (positive) integer m if lambda > a

--
Carl E Mungan, Assoc Prof of Physics  410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363
mailto:mungan@usna.edu ;   http://usna.edu/Users/physics/mungan/
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