Two narrow parallel slits (separated by the distance d = 0.9 mm) are illuminated by monochromatic light with lambda = 550 nm. The two slits create a diffraction pattern of bright and dark spots. Find the smallest angle theta1 (in degrees) at which the rays from the two slits create a bright spot.

   The smallest angle is    

Explanation:

From the question we are told that

  The distance of separation is  d = 0.9 mm

   The wavelength is

General the location of the interference fringes is mathematically represented by

m is the order of the fringe

Now the smallest angle at which both ray create a bright spot would be when

m= 1

Substituting values

its a circle not a square that's simple silly.

explanation: