Make a rule: In general, how do you calculate the energy of a photon that is needed to move an electron between two energy levels?

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid

Atruck driver is attempting to deliver some furniture. first, he travels 8 km east, and then he turns around and travels 3 km west. finally, he turns again and travels 13 km to his destination. what is the drivers total displacement?

What is part of a line has one endpoint and continues in one direction?