JEE Main 1-Sep-2021 Shift 2 Solved Paper

Given, electric field,
E=20‌cos(2×1010t−200x)‌V∕m
Comparing with the standard equation,
E=E0‌cos(ωt−kx)‌V∕m, we get
Wave constant, k = 200
Angular frequency, ω=2×1010‌rad∕s
Speed of the wave, v=

ω

k

=

2×1010

200

=108m∕s
Refractive index, μ=

C

V

=

3×108

108

=3
As we know the relation between the refractive index and dielectricconstant,
μ=√εrμr
Substituting the value in the above equations, we get
3=√εr(1)
εr=9
Thus, the dielectric constant of the medium is 9.