Question

In a young's double-slit experiment, the seventh dark fringe is located 0.028 m to the side of the central bright fringe on a flat screen, which is 1.1 m away from the slits. the separation between the slits is 1.6 × 10-4 m. what is the wavelength of the light being used?

Answer 1

use: dsin(θ) = mλ where d is slit separation, m is fringe order (7), and
θ = tan⁻¹(0.028/1.1) = 1.458deg
Now λ = dsin(θ) /m = (1.6e-4)(sin(1.458))/7 = 5.96e-7 or λ = 596 nm