Ocular refraction and the shadow test . Considerable space has been devoted to the subject of reflectionby mirrors and this indicates its importance. The student is urged not to pass beyond this subject until he hasthoroughly mastered it, practising the formation of images by dia-. Figure 23. mirror. The object L M ;:, C; virtual focus, P. grams drawn by himself ; no matter how poor a draughtsman hemay be, the practice will be valuable. The subject may seem com- c u R E F ACTION plicated at first, but there are only a few important points to under-stand, and it becomes easy. As the retinoscope
Ocular refraction and the shadow test . Considerable space has been devoted to the subject of reflectionby mirrors and this indicates its importance. The student is urged not to pass beyond this subject until he hasthoroughly mastered it, practising the formation of images by dia-. Figure 23. mirror. The object L M ;:, C; virtual focus, P. grams drawn by himself ; no matter how poor a draughtsman hemay be, the practice will be valuable. The subject may seem com- c u R E F ACTION plicated at first, but there are only a few important points to under-stand, and it becomes easy. As the retinoscope is but a plane, or concave mirror, by whichlight is reflected into the eye, causing certain phenomena by whichthe refraction of the eye is estimated, it can readily be appreciated thatthe laws of reflection by mirrors should be thoroughly understood. iVIirrors are surfaces that reflect light in definite directions, aswe have seen, but every body reflects light; rays that are incidentupin a surface, that is irregular, are not regularly reflected, but arereflected in all directions or scattered. Under such conditions lightis said to be diffused no image is created by the reflecting surface. The beam of light composed of the rays R, tigure 24, approachthe surface of C D
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