Question

A laser beam is incident on two slits with a separation of 0.215 mm, and a screen is placed 5.45 m from the slits. an interference pattern appears on the screen. if the angle from the center fringe to the first bright fringe to the side is 0.183°, what is the wavelength of the laser light?

Answer 1

Use: dsin(θ) = mλ  where d is slit separation, m is fringe order (1 here), and 
θ = 0.183
Now λ = dsin(θ) /m = (0.215e-3)(sin(0.183))/1 = 6.867e-7 or λ = 687.7nm  
(red laser)