For 10 points, name these particles, the quanta of light.
The fact that these entities are predicted to have greater-than-unity transmission probability at an infinite potential barrier is the original form of the Klein paradox. That paradox can be resolved in part by noting that, above a cutoff energy, these particles will react with a strong electric field to produce an electron and positron, a phenomenon known as pair production. Spontaneous emission of one of these particles occurs when an electron drops from a higher to a lower energy state, and the energy of one of these particles is given by Planck's constant times the speed of light over wavelength. For 10 points, name these particles, the quanta of light.
The fact that these entities are predicted to have greater-than-unity transmission probability at an infinite potential barrier is the original form of the Klein paradox.
photons [accept gamma rays; prompt on spin-0 particles]