. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE OP SIGHT. 853 Refraction takes place not only through media with plane surfaces, but likewise through media bounded by curved surfaces, for the circum- ference of a circle may be supposed to be made up of a number of infinitely small, straight lines: this is indicated in the case of a lens in Fig. 371. Rays of light passing through a double convex lens in passing in are bent toward the perpendicular (Fig. 372). Now, if the rays thus acted
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE OP SIGHT. 853 Refraction takes place not only through media with plane surfaces, but likewise through media bounded by curved surfaces, for the circum- ference of a circle may be supposed to be made up of a number of infinitely small, straight lines: this is indicated in the case of a lens in Fig. 371. Rays of light passing through a double convex lens in passing in are bent toward the perpendicular (Fig. 372). Now, if the rays thus acted upon be followed they will be found to meet at a point on the opposite side of the lens, called the focus, at which light and heat rays will converge. Rays of light striking the centre of curvature of both surfaces of the lens will pass through unchanged. Such a line is called the chief axis, and the centre of this line is the optical centre of the lens. Rays passing through the optical centre are termed principal or chief rays. Rays parallel with the principal axis of the lens are refracted so that they are collected on the opposite side of the lens at a point called the principal focus; the distance of this point from the central point of the lens is called the focal distance. On the other hand, it is evident that rays diverging from a luminous point at the principal focus will be so refracted. Fig. 373.—Diagram illustrating Action of a Double Convex Lens of High Curvature on Divergent Bays. (Ganot.) The divergent rays from the luminous point, L. are brought to a focus at (behind F, the principal focuB at which parallel rays, S B, converge. as to be parallel when they pass from the lens. Again, rays of light in the principal axis and from a point beyond the principal focus will converge to a point on the opposite side of the lens (Fig. 373). Four cases are possible : First, when the distance of the light from the lens is equal to the focal distance the focus will lie at th
Size: 2598px × 962px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiol, bookyear1890
