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## Homework Statement

Two narrow slits are 0.4 mm apart. The dark fringe of order 5 is 1.2 degrees from the central bright fringe. What is the wavelength of the light in nm?

## Homework Equations

dsin(theta) = (m +1/2)lambda

where d = distance between silts

m=order

lambda = wavelength

## The Attempt at a Solution

It seems simple enough right? I converted the 0.4mm into meters and plugged all the values into the equation which gives me:

(4x10^-4)(sin1.2) = (5 + 1/2)lambda

then lambda = (4x10^-4)(sin1.2)/5.5

Since the answer i get is in meters i have to multiply it by 10^9 right? but that answer is way too big. What am I doing wrong?