A manual of photographic chemistry : including the practice of the collodion process . SIMPLE REFRACTION BY PARALLEL ANDINCLINED SURFACES. I A ray of light, in its passage through any transparentmedium, always travels in a straight line as long as the densityof the medium continues unchanged. But if the density varies,becoming either greater or less, then the ray is refracted,or bent out of the course which it originally pursued. Thedegree to which the refraction or bending takes place dependsmuch upon the nature of the new medium, and in particularupon its density as compared with that of the
A manual of photographic chemistry : including the practice of the collodion process . SIMPLE REFRACTION BY PARALLEL ANDINCLINED SURFACES. I A ray of light, in its passage through any transparentmedium, always travels in a straight line as long as the densityof the medium continues unchanged. But if the density varies,becoming either greater or less, then the ray is refracted,or bent out of the course which it originally pursued. Thedegree to which the refraction or bending takes place dependsmuch upon the nature of the new medium, and in particularupon its density as compared with that of the medium whichthe ray had previously traversed. Hence Water refracts lightmore powerfully than Air, and Glass more so than following diagram illustrates the refraction of a ray of light. The dotted line is drawnperpendicularly to the sur-face, and it is seen that theray of light on entering isbent towards this line. Onemerging, on the otherhand, it is bent to an equalextent away from the per-pendicular, so that it pro-ceeds in a course parallelto, but not coincident with,. ON THE NATURE AND PROPERTIES OF LIGHT. 47 its original direction. If we suppose the new medium, inplace of being more dense than the old, to be less dense, thenthe conditions are exactly reversed,—the ray is bent awayfrom the perpendicular on entering, and towards it on leaving. It must be observed that the laws of refraction apply onlyto rays of light which fall upon the medium at an angle; ifthey enter perpendicularly—in the direction of the dottedlines in the last figure—thdy pass straight through withoutsuffering any refraction. Notice also, that it is at the surfaces of bodies that thedeflecting power acts. The ray is bent on entering, and bentagain on leaving; but whilst it is within the medium it con-tinues in a straight line. Hence it is evident that by variouslymodifying the surfaces of refractive media the rays of lightmay be diverted almost at pleasure. This perhaps will bemade more
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Keywords: ., bookcentury1800, bookdecade1850, bookidgri33125003203441, booksub
