Question

Light of wavelength 550 nm falls on a slit that is 3.50 x 10^-3 mm wide. How far from the central . maximum will the first diffraction maximum fringe be if the screen is 10.0 m away?

Answer 1

Λ$= 550 * 10^{-9}\] m. D = 3.50*10^-6 m.$
$d = 10 m. m = 1 2x = ?$

Then you need to find x when n=1
or 
$sinθ=λ/w=524x10^-9/0.0033=1.59x10^-4$
≈θ for θ<<1 , so θ=$1.59x10^-4 radians$

Then you can find rhe distance of bright fringe from the center:$d= θD=1.59x10^-4x10m ≈ 1.6 mm$