A teacher stands well back from an outside doorway that is 95 cm wide and blows a frequency of 600 Hz. The door faces north. Assume the speed of sound is 340 m/s and that there are no reflections. At what angles (from the line normal to the doorway) is it not possible to hear the whistle outside on the playground?
I've already got the wavelength to be 56.67 cm and I know that i should be applying the double slit equation for destructive interference, but I don't know how to apply that equation for this situation.