N slit interference

In an $N$ slit experiment, waves pass through $N$ narrow slits of each spaced a distance $d$ apart. The interference pattern is observed on a screen that is a distance $L$ from the slits.

$d=$

[m]

$L=$

[m]

$\lambda=$

[nm]

$N=$

The small divisions on the scale on the right represent mm. The more slits there are, the narrower the intensity peaks become. The calculation of the intensity pattern is discussed on the next page.

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$\frac{I}{I_0}$

$y$

Far field

In the far field, where $L > > \lambda$ and $L > > y$, constructive interference will take place when $n\lambda=yd/L$ where $n$ is an integer.