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## Homework Statement

I am to calculated the wavelength of the laser I shone through different slit patterns to create diffraction patters on a screen.

For the single slit diffraction,

Data:

xm is the distance from the central image to the mth minimum.

x1 0.008

x2 0.015

x3 0.023

x4 0.030

x5 0.037

The distance L from the grating to the screen is 1.865

The slit width a is 0.00016

## Homework Equations

asinø=my

Equation for minima for a single slit system

## The Attempt at a Solution

I graphed sinø verses m; in other words:

sinø = (y/a)m

So the slope of that graph is y/a.

So the slope times a is y.

[[ I calculated sinø using (xm)/( ((xm^2)+(L^2))^(1/2) ) ]]

The slope, I found using Excel, of the graph of sinø vs m, is 0.003.

So lambda, y, should be

y = 0.003*0.00016 = 4.8*10^-7

This is a wavelength of 480nm.

The literature value is close to 640nm.

My results for the double-slit is even more off, giving me a calculated wavelength of 2000nm - which is obviously wrong because I wouldn't have been able to see that.

What am I doing wrong?