Air, like water, is made of tiny particles that are too small to see. In fact, air is made up of a mixture of different molecules—nitrogen, oxygen, water vapor, and carbon dioxide, just to name a few. Is this matter or energy? Explain.

The nuclear potential that binds protons and neutrons in the nucleus of an atom is often approximated by a square well. imagine a proton conned in an innite square well of length 105 nm, a typical nuclear diameter. calculate the wavelength and energy associated with the photon that is emitted when the proton undergoes a transition from the rst excited state (n 2) to the ground state (n 1). in what region of the electromagnetic spectrum does this wavelength belong?