Question 208: EM waves

Question

An electromagnetic wave of frequency $\upsilon  = 3.0$ MHz passes from vaccum into a dielectric medium with relative permittivity ${{\varepsilon _r}}$ = 4.0. Then

Accepted Answer

Velocity of electromagnetic wave in vacuum
c = ${1 \over {\sqrt {{\mu _0}{\varepsilon _0}} }}$ = $
u \lambda $
vacuum
.....(1)
Velocity of electromagnetic wave in the medium
v
medium
= ${1 \over {\sqrt {{\mu _0}{\mu _r}{\varepsilon _0}{\varepsilon _r}} }}$ = ${c \over {\sqrt {{\mu _r}{\varepsilon _r}} }}$
For dielectric medium, $\mu $
r
= 1
$ 	herefore $ v
medium
= ${c \over {\sqrt {{\varepsilon _r}} }}$ = ${c \over {\sqrt 4 }} = {c \over 2}$  ........(2)
Wavelength of the wave in medium
$\lambda $
medium
= ${{{v_{medium}}} \over 
u }$ = ${c \over {2
u }}$ = ${{{\lambda _{vaccum}}} \over 2}$

Answer

Wavelength is doubled and frequency becomes half.

Answer

Wavelength is halved and frequency remains unchanged.

Answer

Wavelength and frequency both remain unchanged.

Answer

Wavelength is doubled and frequency unchanged.

EM waves

An electromagnetic wave of frequency \upsilon = 3.0 MHz passes from vaccum into a dielectric medium with relative permittivity {{\varepsilon _r}} = 4.0. Then

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