the lowering of the head,and the knees if female,in performing the wai depends on the relationship between the two persons who are performing the act. The lower the more respect is shown.school students are trained to wai correctly to different people,depending on their relative age and status.
Many people wai in stead of saying “hello” or “thank you” but foreigners need to learn when to wai when not to wai and who to wai. The general rule is the junior porson does the wai first.