Final answer:
The 2nd order aberrations in optics, including spherical aberration and coma, refer to the deviations from ideal imaging caused by imperfections in the optical system's components.
Step-by-step explanation:
The terms for the 2nd order aberrations in optical systems are typically related to the imperfections in the imaging process that lead to deviations from the ideal point-to-point correspondence between the object and its image. In optics, the common 2nd order aberrations include spherical aberration, coma, and astigmatism. Spherical aberration occurs when rays that pass through different parts of the lens are focused at different distances from the lens, leading to a blurred image. Coma happens when off-axis rays focus to form a comet-like blur instead of a point, as highlighted in the provided text. Astigmatism affects rays that pass through the lens at different orientations and results in focused lines at varying distances, further degrading the image quality.
The analysis of these aberrations generally involves complex mathematical expressions that quantify how much the actual image deviates from the theoretical one. This analysis is imperative for the design and testing of optical instruments, like telescopes and microscopes, to ensure the clearest and most accurate images possible.