Question

Would the speed of an em wave be the same in air and in water?

Answer 1

Answer:

All electromagnetic waves travel at the same speed through empty space. For example, light travels more slowly through water than it does through air (see Figure below).

Answer 2

All electromagnetic waves travel at the same speed through empty space. That speed, called the speed of light, is 300 million meters per second (3.0 × 108 m/s). ... For example, light travels more slowly through water than it does through air (see Figure below)