Surface plasmons are collective oscillations of free electrons that occur at the interface between a metal and a dielectric material. These oscillations can be excited by light, leading to enhanced electromagnetic fields at the surface. This phenomenon is crucial in various applications, including sensors and imaging technologies. When light hits a metal surface at a specific angle, it can couple with the surface plasmons, creating a resonance effect. This interaction is utilized in devices like plasmonic sensors and surface-enhanced Raman spectroscopy, which enhance the detection of molecules by amplifying their signals.