a teacher standing in a doorway 1.0 m wide blows a whistle with a frequency of 1000 hz to summon children from the playground. Two boys are playing on the swing 20 m away from the school building. One boy is at an angle of 0 degrees and the other one at 19.6 degrees from a line normal to the doorway. Taking the speed of sound in air to be 335 m/s, which boy may not hear the whistle? Prove your answer.