Modern Physics 7 Question 29

30. An EM wave from air enters a medium. The electric fields are E1=E01x^cos2πνzct in air and

E2=E02X^cos[k(2zct)] in medium, where the wave number k and frequency v refer to their values in air. The medium is non-magnetic.

If εr1 and εr2 refer to relative permittivities of air and medium respectively, which of the following options is correct?

(a) εr1εr2=12

(b) εr1εr2=4

(c) εr1εr2=2

(d) εr1εr2=14

Show Answer

Solution:

  1. v= coefficient of t coefficient of z=1εμ

where, ε=ε0εr and μ=μ0μr.

vairvmed=cc/2=2=μ0ε0μr2εr2μ0ε0μr1εr1εr1εr2=14

Note Medium is non-magnetic.

μr1=μr2



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