Elements of natural philosophy (Volume 2-3) . 2U NATURAL PHILOSOPHY. Fig. 48. Construction of P. Draw p q, paral- thcimageformedlel t p q %{][ ft fc by a reflector; ^7 intersected by Q C,drawn through the op-posite extreme of theobject and opticalcentre, and we havethe image. Let theoptical centre of theeye be at 0; then, de-denoting the visual angle jp 0 q by A, will. Value of visualangle with thereflector; A = qp QP 0Q Oq Eatio of visualangles with andwithout thereflector. and representing, as before, C Q, Cq, and C (9, by /, P 0 f\ and d, respectively, and the visual angle —J^by A\ 6
Elements of natural philosophy (Volume 2-3) . 2U NATURAL PHILOSOPHY. Fig. 48. Construction of P. Draw p q, paral- thcimageformedlel t p q %{][ ft fc by a reflector; ^7 intersected by Q C,drawn through the op-posite extreme of theobject and opticalcentre, and we havethe image. Let theoptical centre of theeye be at 0; then, de-denoting the visual angle jp 0 q by A, will. Value of visualangle with thereflector; A = qp QP 0Q Oq Eatio of visualangles with andwithout thereflector. and representing, as before, C Q, Cq, and C (9, by /, P 0 f\ and d, respectively, and the visual angle —J^by A\ 6 Q we have a f A d-f We shall not stop to discuss this Equation. (70) in practice § 76. We have supposed, in the preceding discussion, distinct vision is distinct vision to be possible for all positions of the eye ; not possible for aii positions of but this we know depends upon the state of convergence the eye; Qr divergence of the rays. If, however, the image, when one is formed, instead of being seen by the naked eye, be viewed by the aid of another lens, so placed that the rays composing each pencil proceeding from the object shall, after the second deviation, be parallel, or within such limits of vergency that the eye can command them, the object will always be seen distinctly, And the image is and either larger or smaller than it would appear to therefo
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