Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
An antenna uses electromagnetic waves of frequency \( 5 \mathrm{MHz} \). For proper working, the size of
the antenna should be :
PhysicsCommunication SystemKCETKCET 2019
Options:
  • A \( 15 \mathrm{~km} \)
  • B \( 15 \mathrm{~m} \)
  • C \( 3 \mathrm{~km} \)
  • D \( 300 \mathrm{~m} \)
Solution:
1425 Upvotes Verified Answer
The correct answer is: \( 15 \mathrm{~m} \)
(B)
\( C=\mathrm{f\lambda} \)
\( \lambda=\frac{C}{f}=\frac{3 \times 10^{8}}{5 \times 10^{6}}=\frac{3}{5} \times 10^{2}=60 \mathrm{~m} \)
The antenna length should be \( \frac{\lambda}{4}=\frac{60}{4}=15 \mathrm{~m} \)

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.