Image result for what does a worm and wheel mechanism do to torque and speed
Like other gear arrangements, a worm drive can reduce rotational speed or transmit higher torque. ... Each full 360 degree turn of a single start worm advances the gear by one tooth. For a multi start worm the gear reduction equals the number of teeth on the gear divided by the number of starts on the worm.
Answer: A crest is the highest point the medium rises to and a trough is the lowest point the medium sinks to. It is also a point on the wave where the displacement of the medium is at a maximum.
