JEE Mains · Physics · STD 12 - 8. Electromagnetic waves
The electric field of a plane electromagnetic wave, travelling in an unknown non-magnetic medium is given by,
\(E_y=20 \sin \left(3 \times 10^6 x-4.5 \times 10^{14} t\right) V / m\)
(where \(x, t\) and other values have S.I. units). The dielectric constant of the medium is __________ .
(speed of light in free space is \(3 \times 10^8 m / s\) )
- A 1
- B 2
- C 3
- D 4
Answer & Solution
Correct Answer
(D) 4
Step-by-step Solution
Detailed explanation
\(n =\frac{ C }{ V }\) \(V =\frac{\omega}{ k }=\frac{4.5 \times 10^{14}}{3 \times 10^6}=\frac{3}{2} \times 10^8\) \(n =2\) \(n =\sqrt{\mu_{ r } \varepsilon_{ r }} \quad\left(\mu_{ r }=1\right)\) \(2=\sqrt{\varepsilon_{ r }}\) \(\varepsilon_{ r }=4\)
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