Calculating Wavelength in Young's Double-Slit Experiment

[MD2000]

In a Young's double-slit experiment, the seventh dark fringe is located 0.023 m to the side of the central bright finge on a flat screen, which is 1.1 m away from the slits. The separation between the slits is 1.5 10-4 m. What is the wavelength of the light being used?
m

I'm having some trouble understanding what exactly the equation is saying. I know I have to use sin theta = mlambda/d for the bright fringe and then sin theta = (m+1/2)lambda/d for the dark..but I'm not sure how to get theta..I figure I need to use the two initial values that I'm given but I'm not sure what those values exactly mean..any help?

 

[Andrew Mason]

In a Young's double-slit experiment, the seventh dark fringe is located 0.023 m to the side of the central bright finge on a flat screen, which is 1.1 m away from the slits. The separation between the slits is 1.5 10-4 m. What is the wavelength of the light being used?
m

I'm having some trouble understanding what exactly the equation is saying. I know I have to use sin theta = mlambda/d for the bright fringe and then sin theta = (m+1/2)lambda/d for the dark..but I'm not sure how to get theta..I figure I need to use the two initial values that I'm given but I'm not sure what those values exactly mean..any help?

Use:
\lambda = \frac{d\sin\theta}{(m+1/2)} where \sin\theta = .023/1.1.

AM

 

[sdekivit]

draw yourself a triangle and note that sin \theta = \frac {d_{minumum-central finge}} {d_{slit-screen}}