Emission of electrons fro Na cathode require less energy (IR rays) while exitaion require more energy (visible rays).?

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

What happens to atoms and chemical bonds during a reaction?

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?