group velocity

例句：

1. 1.The group velocity of the wave is affected by the medium's refractive index.
   波的群速度受到介质折射率的影响。
2. 2.The group velocity of light in a vacuum is approximately 3 × 10^8 meters per second.
   光在真空中的群速度大约是每秒3×10^8米。
3. 3. In this experiment, we measured the group velocity of sound in different materials.
   在这个实验中，我们测量了不同材料中声波的群速度。