The laser pointer emits light because electrons in the material are excited (by a battery) from their ground state to an upper excited state. When the electrons return to the ground state, they lose the excess energy in the form of 521-nm photons. What is the energy gap between the ground state and excited state in the laser material?

The rock in a lead ore deposit contains 89 % pbs by mass. how many kilograms of the rock must be processed to obtain 1.5 kg of pb?

Problem page combustion of hydrocarbons such as pentane ( c5 h12 ) produces carbon dioxide, a "greenhouse gas." greenhouse gases in the earth's atmosphere can trap the sun's heat, raising the average temperature of the earth. for this reason there has been a great deal of international discussion about whether to regulate the production of carbon dioxide.(a) write a balanced chemical equation, including physical state symbols, for the combustion of liquid pentane into gaseous carbon dioxide and gaseous water. (b) suppose 0.350 kg of pentane are burned in air at a pressure of exactly 1 atm and a temperature of 20.0 degree c. calculate the volume of carbon dioxide gas that is produced.be sure your answer has the correct number of significant digits.

Astring vibrates with a frequency of 10 hz. why can't a person hear the sound waves produced by the vibrating string, no matter how large the amplitude of the waves? out! this is homework and due tomorrow! you so much!