The bright-line spectrum of an element in the gaseous phase is produced as 1. protons move from lower energy states to higher energy states 2. protons move from higher energy states to lower energy states 3. electrons move from lower energy states to higher energy states 4. electrons move from higher energy states to lower energy states

The energy released by a nuclear fusion reaction is produced when

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?

What would be the radius of the earth if it had its actual mass but had the density of nuclei? express your answer to two significant figures and include the appropriate units.