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## Homework Statement

Two narrow slits are spaced .25 mm apart and are 60 cm from a screen. what is the distance between the second and third bright lines of the interference pattern if the source is 546 nm of mercury?

## Homework Equations

I used the equation y B (m) = (m[tex]\lambda[/tex]L) / d , where y B (m) is the y coordinate of the bright spot on the interference pattern, m is the spot number (second or third spot), lambda is wavelength, L is the distance from the source to the screen, and d is the distance between the slits.

## The Attempt at a Solution

I converted all given numbers to meters, then found the difference between the y coordinates of the 2nd and third bright spots. I called difference length, the variable we are looking for, x.

x = (3[tex]\lambda[/tex]L) / d - (2[tex]\lambda[/tex]L) / d

x = [3(5.46 x 10^-7 m)(.6 m) / (2.5 x 10^-4 m)] - [2(5.46 x 10^-7 m)(.6 m) / (2.5 x 10^-4 m)]

x = .0039312 m - .0026208 = a difference in the 2nd and third bright spot of .0013104 meters. But, that is barely a width of over a millimeter, I believe something went wrong. Can anyone please help?

Thanks in advance.