Calculating Fringe Positions in Two-Slit Interference Patterns

[Barry Melby]

Homework Statement

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Light passing through a two-slit grating makes a pattern on a screen located 500 mm away. In this pattern, the fifth-order dark fringe is 45.0 mm from the central bright fringe. How far from the central bright fringe is the third-order bright fringe?

Homework Equations

This is what I'm looking for help on.

The Attempt at a Solution

I'm not even sure which equations to use to solve this. Any ideas?

 

[Khashishi]

You got a textbook you are working with? Is there a section on two slit interference (aka Young's double slit experiment)? What equation does it give there?

 

[Barry Melby]

it's not in my book. any ideas?
How do i go about this with a dark fringe and a bright fringe if i don't know the wavelength or slit width?GOT IT.