What Is the Distance Between the Slits in Young's Double Slit Experiment?

[idkgirl]

Homework Statement

Light from a sodium lamp (\lambda \; =\;589\;{\rm nm}) illuminates two narrow slits. The fringe spacing on a screen 150{\rm cm} behind the slits is 4.0{\rm mm} .

Homework Equations

I think I should use: d*(y/L) = m(λ)

The Attempt at a Solution

I did: d = 1(5.89e-7)*(1.5/.0044)
I changed everything to meters so later I can convert to mm.

 

[Simon Bridge]

Light from a sodium lamp $\lambda \; =\;589{\rm nm}$ illuminates two narrow slits. The fringe spacing on a screen $150{\rm cm}$ behind the slits is $4.0{\rm mm}$

... presumably you want to find the slit spacing?

I think I should use: d*(y/L) = m(λ)

If you are unsure, sketch the setup and use geometry.

There are special conditions for the use of that equation - do you know what they are?
(If not, go back to the geometry.)

I did: $d = (1)\cdot(5.89\times 10^{-7})\cdot(1.5)/(0.0044)$
I changed everything to meters so later I can convert to mm.

... or you could just convert everything to millimeters right at the start?

So far so good - so... did you have a question?

 

[idkgirl]

Yeah, I figured it out. I think I was probably just entering things in my calculator strangely.

Thankya ^^

 

[Simon Bridge]

Ah yes - I've seen people enter the same set of numbers into a calculator three times and get three different answers. It can be so bad that some people will keep punching the same calculation in until they get an answer they like and then stop.

This is why calculators in banks have such big buttons... you'd think it would be the same for engineers wouldn't you?

But at least you did the algebra first and the arithmatic last.
Well done.