The minimum size of an antenna for transmitting electromagnetic waves at $1500 \mathrm{MHz}$ is

The minimum size of an antenna for transmitting electromagnetic waves at $1500 \mathrm{MHz}$ is
  1. $2 \mathrm{~cm}$
  2. $5 \mathrm{~cm}$
  3. $2 \mathrm{~m}$
  4. $200 \mathrm{~cm}$

Solution

Minimum size of transmitting antenna, $\begin{aligned} l & =\frac{\lambda}{4}=\frac{c / f}{4} \\ \Rightarrow l & =\frac{3 \times 10^8}{4 \times 1500 \times 10^6}=\frac{3 \times 25}{1500}=\frac{1}{20} \mathrm{~m} \\ & =\frac{100}{20} \mathrm{~cm}=5 \mathrm{~cm} \end{aligned}$

Asked in: AP EAMCET 2022 (07 Jul Shift 2)

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