Assertion: c | /r/HasProperty | 1.5 ≈
Facets:
Source sentences:
text: For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200000 km/s (124000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 299700 km/s (186220 mi/s), which is about 90 km/s (56 mi/s) slower than c.