This is called the index of refraction. When light crosses the boundary between mediums (media) with different indices, it is bent (refracted).
It's usually defined the other way around ... the ratio of the speed of light in vacuum to its speed in the medium. Since the speed of light is greater in vacuum than in any medium, the number is always greater than 1. It's referred to as the "refractive index" of the medium.
The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium.
The index of refraction.
In a rough, round figure? 930,000 to 1. Sound travels roughly 1/5 of a mile per second in air. Light travels 186,000 miles per second in a vacuum. In five seconds sound travels one mile. In five seconds, light travels 930,000 miles in a vacuum.
The two are very different....
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It is usually expressed the other way: the ratio of the speed of light in a vacuum to the speed of light in a medium. In that case, it is called the "index of refraction".
The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium.
Refractive index of the medium is defined as the ratio of the velocity of light in vacuum to that in the medium. No unit for refractive index.
Refractive index is the ratio of speeds.
Refractive index refers to the velocity of light's ratio in a vacuum to its velocity under a specified medium.
Refractive Index: the ratio of the velocity of light in a vacuum to that in the given medium
The substance's index of refraction isSpeed of light in vacuum / Speed of light in the substance
The speed of light is a set speed at which all electromagnetic waves travel at in a vacuum. It is 3*10^8 meters/second... That being said, when light, or any other EM wave, travels through a medium it will slow down. Every material has an index of refraction which is the ratio of the speed at which light travels in a vacuum, to the the speed it travels in that material. If you know the index of refraction, you can use Snell's law to determine the speed light will travel through a specific medium. Every medium is different, however a rule of thumb is the denser the medium, the slower light will travel through it. For example, light travels faster in the atmoshpere than it does in water.
The relationship is the following: the speed of light in an object is equal to the speed of light in a vacuum, divided by the material's index of refraction. Example: A certain glass has an index of refraction of about 1.5 (it depends a bit on the type of glass!). Since the speed of light in a vacuum is 300,000 km/sec., the speed of light in such glass is (300,000 km/sec) / 1.5 = 200,000 km/sec.
The speed of light in a vacuum is 186,000 miles per second and the speed of sound at 70 degrees F at sea level is approx. 1100 feet per second. Do the math. You should come up with something around 879 thousand. (a ratio, with no units)
The index of refraction.
Refractive indices, n, have no units because they are ratios. They are the ratio of the speed light in a vacuum C, (~3x108m/s) to speed of light in the medium vm. Therefore: