Answer:
Speed of an EM wave is different in air and in water.
Step-by-step explanation:
The speed of an EM wave is different in air and water .
Since the frequency of any EM wave is its characteristic property, therefore wavelength and speed of EM wave Change on changing the medium of propogation.
Also the refractive index
of any medium is defined as the ratio between light's speed in vacuum to the light's speed in any medium.
Also ,it can be define as speed of any EM wave in any medium = c/refractive index of medium.
Here, c is the speed of light,
.