Calculate the speed of light traveling through diomond(n diomond =2.42)

The relationship between the refractive index ($n$), the speed of light in vacuum ($c$), and the speed of light in the medium ($v$) is given by:

$$n = \frac{c}{v}$$

The speed of light in vacuum ($c$) is approximately $3.00 \times 10^8 \ \text{m/s}$.
The refractive index of diamond ($n$) is given as 2.42.

$$v = \frac{3.00 \times 10^8 \ \text{m/s}}{2.42}$$

Given values have three significant figures ($3.00 \times 10^8$ and 2.42), so the result should also be rounded to three significant figures.

$$v \approx 1.24 \times 10^8 \ \text{m/s}$$