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## Homework Statement

Light passes through a 200 line/mm grating and is observed on a 1.0 m wide screen located 1.0 m behind the grating. Three bright fringes are seen on both sides of the central maximum. What are the minimum and maximum possible values of wavelength?

## Homework Equations

d= 1mm/200 lines = 5.0e-6 meters

## The Attempt at a Solution

I think I got the maximum value:

The maximum value is where the m=3 bright fringe is on the edge of the screen, so the angle is arctan(.5/1) theta= 26.56 degrees. Then dsin(theta)=m*lambda

(5.0e-6)sin(26.56)=3* lambda lambda= 7.45e-7 meters= 745 nm

But for the minimum, I can't figure out what kind of relationship to set up.