Question

A half wave dipole at a frequency of 100 MHz has a length of ________.

• A. 100 m
• B. 3 m
• C. 1.5 m
• D. 0.75

Hint:

For a half-wave dipole, always remember: \( L = \frac{\lambda}{2} \), and \( \lambda = \frac{c}{f} \). Just compute wavelength first and divide by 2.

Answer 1

The Correct Option is C

We are given:
- Frequency \( f = 100\ \text{MHz} = 100 \times 10^6\ \text{Hz} \)
- We are to find the length of a half-wave dipole.
Step 1: Use speed of light formula.
The wavelength \( \lambda \) of an electromagnetic wave is given by: \[ \lambda = \frac{c}{f} \] where \( c = 3 \times 10^8\ \text{m/s} \) (speed of light in vacuum).
Substitute the values: \[ \lambda = \frac{3 \times 10^8}{100 \times 10^6} = 3\ \text{meters} \] Step 2: Use half-wave dipole formula.
For a half-wave dipole antenna, the length \( L \) is:
\[ L = \frac{\lambda}{2} \] So, \[ L = \frac{3}{2} = 1.5\ \text{meters} \] \[ \boxed{L = 1.5\ \text{m}} \]