In what substance in Table 25.1 is the speed of light $2.290\times 10^8\text{ m/s}$?

Video Transcript

This is College Physics Answers with Shaun Dychko. The speed of light in a substance is 2.290 times 10 to the 8 meters per second and the question is what is the substance? Well we can figure out the index of refraction of the substance by taking the speed of light in a vacuum dividing it by the speed in this substance. So that's 2.998 times 10 to the 8 meters per second divided by 2.290 times 10 to the 8 meters per second and we get an index of refraction of 1.309. So we can look at our table [25.1] and find some material that has that index of refraction and here it is: ice at 20 degrees Celsius has an index of refraction of 1.309. So the substance must be ice at 20 degrees Celsius.