The microscope and its revelations . ipal focus (as thefocus for parallel rays is termed) of a double-cojiYQX. lens to beat the distance of its radius, that is, in its centre of curvature,and that of a ^too-convex lens to be at the distance of twiceits radius, that is, at the other end of the diameter of itssphere of curvature. 5. It is evident from what has preceded, that as a double 42 OPTICAL PRINCIPLES OF THE MICEOSCOPE. convex lens brings parallel rays to a focus in its centre ofcurvature, it will on the other hand cause those rays toassume a parallel direction, which are diverging from t
The microscope and its revelations . ipal focus (as thefocus for parallel rays is termed) of a double-cojiYQX. lens to beat the distance of its radius, that is, in its centre of curvature,and that of a ^too-convex lens to be at the distance of twiceits radius, that is, at the other end of the diameter of itssphere of curvature. 5. It is evident from what has preceded, that as a double 42 OPTICAL PRINCIPLES OF THE MICEOSCOPE. convex lens brings parallel rays to a focus in its centre ofcurvature, it will on the other hand cause those rays toassume a parallel direction, which are diverging from thatcentre before they impinge upon it (Tig. 2); so that, if aluminous body be placed in the principal focus of a double-convex lens, its divergent rays, falling on one surface of thelens as a cone, will pass-forth from its other side as a , if rays already converging fall upon a double-convexlens, they will be brought together at a point nearer to itthan its centre of curvature (Eig, 3); whilst, if the incident Fig. Eays already convcrtrinu-, brousrht-together at a point nearer thanthe principal focus ; and rays diverginijc from a point within the prin-cipal focus, still diverging, though in a diminished degree. rays be diverging from a distant point, their focus will be moredistant from the lens than its principal focus (Fig. 4). The
Size: 1986px × 1258px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
