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JEE Mains · Physics · STD 12 - Electromagnetic waves
  • JEE Mains 2022
  • Medium
  • Numerical

An antenna is placed in a dielectric medium of dielectric constant \(6.25\). If the maximum size of that antenna is \(5.0\, mm\). it can radiate a signal of minimum frequency of \(GHz .\) (Given \(\mu_{ r }=1\) for dielectric medium)

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Correct Answer

(B) \(6\)

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Detailed explanation

\(C^{\prime}=\frac{C}{\sqrt{\mu_{r} \varepsilon_{r}}}=\frac{3 \times 10^{8}}{\sqrt{6.25}}=\frac{3 \times 10^{8}}{2.5}\)

\(f \lambda=1.25 \times 10^{8} s\)

\(\Rightarrow f \left(5 \times 10^{-3} \times 4\right)=1.25 \times 10^{8}\)

\(f =6.25 \,GHz\)

So \(f \approx 6\)

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