An electromagnetic wave of frequency 3 ~MHz passes from vacuum into a dielectric medium ( _r=1) of relative permittivity 4.0. Then,

Step-by-step solution

The frequency of an electromagnetic wave is determined by the source and remains constant when the wave travels from one medium to another. Thus, the frequency remains 3 MHz . The speed of an electromagnetic wave in vacuum is c = 1 ₀ ₀ . In a dielectric medium with relative permittivity _r and relative permeability _r , the speed is v = 1 ₀ _r ₀ _r = c _r _r . Given _r = 1 and _r = 4.0 , the speed in the medium is v = c 1 4.0 = c 2 . The wavelength in a medium is given by ' = v f . Since v = c 2 and f is constant,