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Physical Chemistry

Ordinary ray

Definition and meaning of Ordinary ray in chemistry.

The ordinary ray is the specific component of light in a birefringent crystal that completely obeys the standard laws of refraction, including Snell's law.

In more detail

When a beam of unpolarized light enters an anisotropic crystal at an angle to the optic axis, it splits into two distinct rays due to the phenomenon of birefringence. The ordinary ray travels at a constant velocity in all directions within the crystal, which means its refractive index remains completely constant regardless of its propagation direction. In contrast, the accompanying extraordinary ray has a velocity and refractive index that vary depending on its direction of travel relative to the optic axis.

Key facts

FieldPhysical Chemistry
FormulaCaCO3
Velocity behaviorConstant in all directions
CounterpartExtraordinary ray
Example

When observing an object through a piece of transparent calcite (CaCO3), the stationary image that does not shift when the crystal is rotated is formed by the ordinary ray.

Frequently asked questions

How does the ordinary ray differ from the extraordinary ray in practical terms?

The ordinary ray has a fixed refractive index and perfectly obeys Snell's law, while the extraordinary ray's path deviates depending on the viewing angle.

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