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?
dsin(theta) = (m +1/2)lambda
where d = distance between silts
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?