Determining hole size using laser interference

[Drizzy]

Homework Statement

Lisa makes a hole in aluminum foil. She wants to know the diameter of the hole. She points a laser through the hole. That picture is what appears on the wall that is 1,25 meters behind the aluminum. the distance between every circle is 8mm. the wave length is 633nm.

http://imgur.com/a/kcaPz

Homework Equations

dsinx=kλ

The Attempt at a Solution

[/B]
8mm between maximum 1 and 2. so I know that Tanx= 0.0008/1.25
x= arcTan(0.008/1.25)
d=kλ/sinx
d= 1*633*10^-9/(sin(arcTan(0.008/1.25))

I get the wrong answer, why?

 

[BvU]

What do you get for the sin(arcTan(0.008/1.25) ?

 

[Drizzy]

0.0063998689

 

[BvU]

Ok, so degrees and radians isn't the problem and I have to read the problem statement. Is your formula applicable for a single hole (as opposed to two slits) ?

 

[Drizzy]

yes

 

[Tom.G]

Check your value of "k".

Also, is there a slipped decimal in:

distance between every circle

 

[Cutter Ketch]

Two things.

First, perhaps for learning purposes your class is using that simple equation, but that is not the correct equation for the ring spacing of an Airy disk. Are you sure your class didn't discuss Airy rings and present a slightly different formula?

Second, the distance to the first Airy minimum is different than the spacing of subsequent minima. You have to go above the first order to answer correctly.