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Ch. 7: Optical Properties

Ch. 7: Optical Properties Page of 187 Ch. 7: Optical Properties Text size:minus plus Restore normal size   Mail page  Print this page
When light travels from one medium to another, there is in general an increase or decrease in velocity, which results in the phenomenon of refraction, i.e. a change in the direction of propagation. In the case of transparent gems, the reflected light is not so important as the refracted light. When a ray of light passes into water obliquely, the path of the ray is not straight, but bent. When a ray of light travels from a rarer to a denser medium, as in the above case, the ray is bent towards the normal to the plane of contact between the two media. Naturally, the reverse will be the case when a ray of light travels from a denser to a rarer medium. It is then bent away from the normal. In fig. 27 the angle of incidence CXO is called i and the angle of refraction DXN as r. The law of.
refraction is: The incident and refracted rays lie in the same plane, and the ratio of the velocities in the two media, and the ratio between the sines of the angles of incidence and refraction, i and r, are constant for the media concerned.
The constant is the index of refraction, the velocity of light in air being l.
For water R.I. = 1-333 and for diamond 2-42. It is evident that gem-stones could be identified by the deter-
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Ch. 7: Optical Properties Page of 187 Ch. 7: Optical Properties
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