 Baierlein asks us to consider an atom that emits two photons of equal energy “back-to-back” in opposite directions. Although Baierlein uses the Planck-Einstein expression \(E = hf\) for the energy of a photon, where \(f\) is its frequency, and \(h\) is Planck’s constant, as he himself points out the right-hand side of that expression does not figure significantly in his derivation. Baierlein’s derivation, he tells us, works in exactly the same way if we just think of an object that emits two “bursts” of light construed as classical electromagnetic radiation. We will adopt this latter approach and consider a body \(B\) that emits two bursts of light in opposite directions, each with an energy \(E/2\) (this is the approach Norton 2014 uses). The total energy emitted by \(B\) is therefore simply \(E\). 