1. Wave - Particle Duality

2. Evidence ; Wave Model Particle Model DiffractionPhotoelectric Effect InterferenceSpectrometry Polarisation Refraction Reflection => QUANTUM THEORY OF RADIATION

4. Duality zALL physical entities may be described as either WAVES or PARTICLES (Duality) zLinked by two equations ; E = hf p = h   (De Broglie equation) E, p - particle phenomena f, - wave phenomena as predicted by Einstein Special Theory of Relativity, h = Planck constant = 6.6 x 10 -34 Js

6. Some more Maths zconsider a photon ; p = h/,E = hf, c = f p = h/ = hf/c = E/c => E = pc but, p = mc (momentum = mass x velocity) => E = mc 2

7. What does it mean ? zWhen a photon is considered as a particle, its mass may be taken as equal to ; zm = E/c 2 = hf/c 2 zthis ‘mass/energy equivalence’ is only significant in nuclear physics.