21.3 The Dual Nature of Light

• While it is strange to think of a massless particle exhibiting momentum, it is now a well-established fact within the scientific community. Macroscopic evidence of photon momentum
• For the discovery of this conserved scattering, now known as the Compton effect, Arthur Compton was awarded the Nobel Prize in 1929
• We call this twofold nature the particle-wave duality, meaning that EM radiation has properties of both particles and waves
• Compton scattering provided evidence that photon-electron interactions abide by the principles of conservation of momentum and conservation of energy.
• The momentum of individual photons, quantified by 𝐩=ℎ𝜆p=hλ, can be used to explain observations of comets and may lead to future space technologies.
• Electromagnetic waves and matter have both wave-like and particle-like properties. This phenomenon is defined as particle-wave duality.