Alabel for a plant is made of copper. when it is first put in a garden, it is bright and shiny. after a few months, the label has a dull, greenish color. when you rub your finger over the surface, some soft material rubs off. what happened to the copper?

Awoman stands a distance d from a loud motor that emits sound uniformly in all directions. the sound intensity at her position is an uncomfortable 2.0×10-3 w/m2. at a distance 2.6 times as far from the motor, what are (a) the sound intensity and (b) the sound intensity level relative to the threshold of hearing?

An electric power distributor charges residential customers $0.10 per kilowatt-hour (kwh). the company advertises that "green power" is available in 150 kwh blocks for an additional $4 per month. (green power is generated from solar, wind power, and methane sources.) if a certain customer uses an average of 391 kwh per month and commits to one monthly 150 kwh block of green power, what is her annual power bill

Two waves maximally constructively interfere at a point in space. among the options below, select the possible value of their phase difference at that point in space.a. zerob. πc. π/2d. not determinable by the information provided