2. Momentum & Pressure
EM waves carry momentum. When light hits an object, it transfers this momentum, exerting a tiny but measurable force.
Perfect Absorption: $P = I/c$
Momentum is fully transferred as the surface stops the wave.
Perfect Reflection: $P = 2I/c$
The "bounce" (direction change $\Delta p$) doubles the total momentum transfer.
Surface Interaction
Wave Intensity ($I$)
1.5
Wave: Energy Flux (Continuous Field)
Particles: Photons (Momentum Packets)
Energy Flux $\rightarrow$ Momentum Transfer $\rightarrow$ Force