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Slit & light interference

by quicksilver123
Tags: interference, light, slit
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quicksilver123
#1
Jan31-13, 10:57 AM
P: 91
1. The problem statement, all variables and given/known data

Two narrow slits are cut into a sheet of paper and set in front of a laser beam, causing an interference pattern to appear on the wall.
If the distance from one slit to the third bright fringe is 0.5000004 m
and the distance from the other slit to the same bright fringe is 0.5000008 m
calculate the wavelength of the light from the laser.

2. Relevant equations

| PmS1 - PmS2 |= m[itex]\lambda[/itex]

3. The attempt at a solution

My answer:

|0.5000004-0.5000008|=(3)[itex]\lambda[/itex]
0.0000004/3 = [itex]\lambda[/itex]
[itex]\lambda[/itex] = 0.000000133 m

edit: my answer uses
| P3S1 - P3S2|
whereas the book's answer uses
| PmS1 - PmS2|

How would I turn one into the other?

The book's answer:

|0.50000030-0.50000165|=3[itex]\lambda[/itex]
[itex]\lambda[/itex]=0.00000135/3
[itex]\lambda[/itex]=0.00000045m = 450nm

I'd like to know where they got the values of:

PmS1=0.50000030m
and
PmS2=0.50000165m
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TSny
#2
Jan31-13, 11:03 AM
HW Helper
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P: 4,743
Quote Quote by quicksilver123 View Post
If the distance from one slit to the third bright fringe is 0.000004 m
and the distance from the other slit to the same bright fringe is 0.000008 m
Did you leave out the "5" after the decimal points? Your work looks correct to me. I don't see where the book's numbers come from either.
quicksilver123
#3
Jan31-13, 11:04 AM
P: 91
didn's leave anything out :/


sorry, i edited my original post a second ago.


edit: my answer uses
| P3S1 - P3S2|
whereas the book's answer uses
| PmS1 - PmS2|

How would I turn one into the other?

TSny
#4
Jan31-13, 11:09 AM
HW Helper
Thanks ∞
P: 4,743
Slit & light interference

Quote Quote by quicksilver123 View Post
didn's leave anything out :/


sorry, i edited my original post a second ago.
Is the distance from the first slit to the bright fringe 0.000004 m or 0.500004 m?

edit: my answer uses
| P3S1 - P3S2|
whereas the book's answer uses
| PmS1 - PmS2|

How would I turn one into the other?
Let m = 3?
quicksilver123
#5
Jan31-13, 11:14 AM
P: 91
sorry, corrected the mistake.

the book has been known to make errors in their solutions... but i was wondering if there's something i'm missing
TSny
#6
Jan31-13, 11:26 AM
HW Helper
Thanks ∞
P: 4,743
I think your work is correct.
quicksilver123
#7
Jan31-13, 11:27 AM
P: 91
alright, thanks


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