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REFRACTION OF LIGHT.

those rays which pass nearest the edges of the knives, have beendrawn from their former direction towards the knives. Thisproperty of light is called inflection. The edge of any other thinplate of metal produces the same effect.

Experiment II.

If we let a beam of light pass into a dark room through a nar-row slit made in a window-shutter, not above part of aninch broad, the beam of light will be split into two, and leave adark space in the middle, it will therefore be attracted by bothsides of the slit.

Experiment III.

The shadow of a small body, as a hair, a thread, See. placedin a beam of the sun's light, will be much broader than itought to be if the rays of light passed by these bodies in rightlines, or without being attracted by them.

6. REFRACTION OF LIGHT.

When a ray of light passes through the same medium, orwhen it passes perpendicularly from one medium to another, itcontinues to move on, without changing its direction. But thecase is different when it passes obliquely from one medium toanother of a different density; it is then bent from its first direc-tion and assumes a new one; it is said to be refracted. When itpasses into a denser medium, it is refracted tou ards the per-pendicular; but when it passes into a rarer medium, it is re-fracted from the perpendicular.

The denser the medium, the more the rays are bent, and ap-proach to a perpendicular let fall upon its surface.

This however must always be understood of the rays whichfall obliquely upon these media, for those rays which fall per-pendicularly do not suffer any deviation ; refraction only takesplace when the rays fall obliquely, and is so much greater