Ocular refraction and the shadow test . If the same experiment be made with a cylindrical lens,the line will appear to break at the edges of the lens and to oscillate,swinging to a certain distance and then back again. Figure 83 willillustrate the effect created; I, shows the appearance of the verticalstraight line see 1 through a convex cylinder; II, the same line seenthrough a concave cylinder. Comparison shows that the direction of LENSES. 8i the motion of oscillation is the reverse with a convex to what it iswith a concave. In making this experiment it will be noticed that intwo positions,
Ocular refraction and the shadow test . If the same experiment be made with a cylindrical lens,the line will appear to break at the edges of the lens and to oscillate,swinging to a certain distance and then back again. Figure 83 willillustrate the effect created; I, shows the appearance of the verticalstraight line see 1 through a convex cylinder; II, the same line seenthrough a concave cylinder. Comparison shows that the direction of LENSES. 8i the motion of oscillation is the reverse with a convex to what it iswith a concave. In making this experiment it will be noticed that intwo positions, as the lens is rotated, the vertical straight line willappear unbroken as seen by A and B, figure 84. This applies to bothconvex and concave cylinders, no difference in them will be detectedif each be placed in these positions. In the illustrations the cylindrical lenses shown are purposelytaken from the test cases, to make it as easy as possible for the stu-dent to understand; their action is exactly the same as other
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