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Since the energy of a photon is quantized, does it mean that its energy is not divisible?


That is exactly right. Quantization means that it is the smallest discrete entity--that there exists no smaller elementary particle.

Matt Voss

An isolated photon, say coming from a distant galaxy can travel inter-galactic distances without having its energy change. The energy given by: E = h x (nu) where E is the energy, (nu) is the frequency and 'h' is Plank's constant. However, a photon that interacts with matter by various mechanisms such as, scattering, absorption, reflection, and many others. Then the photon loses its identity. For example, you cannot put a tag or label on a photon that is absorbed by an atom or molecule. Other photons of the same or lesser energy (lower frequency). However, there is no way to know that those emitted photons are the same as the incident photon. This is a general rule. For example a neutron can decay into a proton and an electron (and also an anti-neutrino). But the neutron is not simply the sum of the particles. As long as the electron, proton, and anti-neutrino reside in the neutron they do not have separate identities. They are in fact a combination of quarks held together by gluons.

Vince Calder

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