An antenna is placed in a dielectric medium of dielectric constant 6.25 . If maximum size of that an

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8.Electromagnetic waves

medium

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)

A

$60$

B

$6$

C

$9$

D

$3$

(JEE MAIN-2022)

Solution

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

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

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

$f =6.25 \,GHz$

So $f \approx 6$

Standard 12

Physics

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