光和聲音在移動的介質中的速度

The main difference between light and sound waves is the former is electromagnetic wave and the latter is a mechanical wave.

Transmission of a mechanical wave requires a medium. Hence, if the medium is moving, the speed of the wave will be altered. For example, if a wind is blowing in the same direction as that of the sound, the sound speed will increase.

Electromagentic wave doesn't need a medium to propagate. Hence, its speed is independent of the speed of the medium.

Q: 除了光外,有沒有其他波可以在真空中傳播?
A: All eelctromagentic waves can travel in vacuum. Light is only a small portion of the electromagentic spectrum. Waves from all other portions of the spectrum, e.g. radio wave, microwave, infrared, ultraviolet, x- and gamma rays, can travel in vacuum.