A Pair of Narrow Slits That Are $1.8 \mathrm {~mm}$ Apart Is Illuminated by a Monochromatic Coherent Light Source

Multiple Choice

A pair of narrow slits that are $1.8 \mathrm {~mm}$ apart is illuminated by a monochromatic coherent light source. A fringe pattern is observed on a screen $4.8 \mathrm {~m}$ from the slits. If the wavelength of the monochromatic light is $450 \mathrm {~nm}$ , what is the angular separation between adjacent dark fringes on the screen, measured in milliradians?

A) $0.30 \mathrm { mrad }$
B) $0.25 \mathrm { mrad }$
C) $0.15 \mathrm { mrad }$
D) $0.36 \mathrm { mrad }$
E) $0.20 \mathrm { mrad }$