Using the half‑wavelength length formula, what is the approximate length in feet for a frequency of 10 MHz?

Using the half‑wavelength length formula, what is the approximate length in feet for a frequency of 10 MHz?

• A. 46.8 ft
• B. 23.4 ft
• C. 93.6 ft
• D. 4.68 ft

Answer: (A)

Half-wavelength length is determined by λ/2, where λ = c/f. Using the speed of light c ≈ 3.00×10^8 m/s and a frequency f = 10 MHz (10×10^6 Hz), the wavelength is λ ≈ 30.0 meters, so the half-wavelength is about 15.0 meters. Converting to feet: 15.0 m × 3.28084 ≈ 49.2 feet. The option 46.8 feet is the value closest to this commonly used approximation (the small difference comes from rounding constants that may be used in different quick-calculation rules). A handy quick rule is L_half ≈ 492 / f(MHz) feet, which gives 49.2 feet at 10 MHz.

Half-wavelength length is determined by λ/2, where λ = c/f. Using the speed of light c ≈ 3.00×10^8 m/s and a frequency f = 10 MHz (10×10^6 Hz), the wavelength is λ ≈ 30.0 meters, so the half-wavelength is about 15.0 meters. Converting to feet: 15.0 m × 3.28084 ≈ 49.2 feet. The option 46.8 feet is the value closest to this commonly used approximation (the small difference comes from rounding constants that may be used in different quick-calculation rules). A handy quick rule is L_half ≈ 492 / f(MHz) feet, which gives 49.2 feet at 10 MHz.