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

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

measure their densities same density, same sub

a is the best answer your welcome

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods