You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.

The speed of light in a medium is determined by its refractive index (n). The refractive index is a measure of how much the speed of light is reduced when it travels through a particular medium compared to its speed in a vacuum.

The speed of light in a medium is given by the equation:
v = c/n
where:
» v is the speed of light in the medium,
» c is the speed of light in a vacuum,
» n is the refractive index of the medium.

The higher the refractive index, the slower the speed of light in that medium.

In general, the refractive index of kerosene and turpentine is closer to that of air, which is approximately 1.00. On the other hand, water has a higher refractive index (around 1.33).

Since the refractive index is in the denominator of the speed equation, a higher refractive index corresponds to a slower speed of light in the medium. Therefore, light would travel fastest in the substance with the lowest refractive index. In this case, that substance is likely to be either kerosene or turpentine.

Without specific refractive index values for kerosene and turpentine, it’s not possible to determine which one allows light to travel faster. However, both are likely to have similar speeds of light, and both would be faster than light in water.