Coherent microwaves of wavelength 5.00 cm enter a tall, narrow window in a building otherwise essentially opaque to the microwaves. if the window is 36.0 cm wide, what is the distance from the central maximum to the first-order minimum along a wall 6.50 m from the window?

The solution for this problem is:

For 1st minimum, let m be equal to 1. 

d = slit width

D = screen distance. 

Θ = arcsin (m * lambda/ (d))

= 0.13934 rad, 7.9836 deg 

y = D*tan (Θ)

y = 6.50 * tan (7.9836)

= 0.91161 m is the distance from the central maximum to the first-order minimum