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1 year ago in Physics , Quantum Gravity By Ankur
What is the smallest possible electromagnetic wavelength‑ The Planck length?
In electromagnetics, we learn wavelength can be arbitrarily small as frequency increases. But at extreme energies, quantum gravity effects should become significant. Does this imply the Planck length is a hard cutoff for EM waves, or does the effective theory break down before that? I'm trying to reconcile classical EM with Planck-scale limits.
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By Sourabh Answered 1 year ago
This is a frontier question. In standard quantum field theory, there's no lower limit; you can have arbitrarily high energy (short wavelength) photons. However, the concept of a "wavelength" smaller than the Planck length becomes meaningless, as spacetime itself is expected to become quantized or foamy. I would recommend thinking of it not as a hard cutoff, but as an energy scale where our theory breaks down. Around the Planck energy (~10^19 GeV), the photon would likely cease to be a well-defined particle in a smooth spacetime, and a theory of quantum gravity would be needed to describe it.
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