Technical optics employs distinct models to describe optical phenomena in instruments. \(\bullet \)   Geometrical Optics models light as rays. In a uniform, isotropic medium, these rays travel in straight lines. When encountering reflection, refraction, or a non-uniform medium, their paths bend to minimize propagation time. \(\bullet \)   Wave Optics describes light as a transverse electromagnetic wave. This framework is essential for understanding diffraction, which fundamentally limits the resolution of imaging systems. \(\bullet \)   Quantum Optics treats photons as entities with both wave-like and particle-like properties (wave-particle duality), where a photon’s energy and momentum are determined by its wavelength. All three models are utilized in the design and analysis of optical systems, with each providing critical insight into different aspects of system performance.