Light travels at different speeds in different materials. In air, or the vacuum of space, it travels very fast (about 299,792,458 meters per second). In water, light travels 1 and one third slower than it does in air. We say water has a refractive index of 1.33.
Material | Index | |
Quartz | 1.54 | |
Salt | 1.54 | |
Mineral oil | 1.48 | |
Corn oil | 1.47 | |
Glycerine | 1.47 | |
Ethanol | 1.36 | |
Water | 1.33 | |
Ice | 1.31 | |
Air | 1.00 |