Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to make a laser [title] Provide a source of energy. [step] Lasers work, or " lase, " by stimulating electrons to emit light of a particular wavelength. ( this process was first proposed in 1917 by albert einstein.

Ending1: ) for electrons to emit light, they must first absorb energy to boost them to a higher orbit, then discharge that energy as light when returning to their original orbit. These energy sources are known as " pumps. Ending2: You could get a laser for just about $150). Then, as it turns out, the laser produces a shockwave that wakes us up. Ending3: ) the exact purpose of an operating laser is not entirely understood, but it is certainly becoming an element of the history and development of lasers, because heated and cooled ions are present. [substeps] How energy is pumped through your lasers either indirectly or through heat sources such as ash, furnaces, and other sources. Ending4: ) these disks have a program called bok dum that is considered extremely efficient at shutting down certain types of electronic components. Nearly every light source in human bodies processes separate the cores of electrons from the kernel and extract electrons from their combustion centers in the scientist's tube, in order to actually perform energy energy.

Answer format: ending1/ending2/ending3/ending4