An 800-KHz Radio Signal Is Detected at a Point 8

question 3

Multiple Choice

An 800-kHz radio signal is detected at a point 8.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.90 V/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the average electromagnetic energy density at that point? (c = 3.0 x 10⁸ m/s, μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

• A) 3.6 pJ/m³
• B) 5.1 pJ/m³
• C) 7.2 pJ/m³
• D) 10 pJ/m³
• E) 14 pJ/m³

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Definitions:

Mousterian Toolmakers

Prehistoric peoples associated with the Middle Paleolithic period, known for their stone tool technology used by Neanderthals and early modern humans.

Scraper

A tool used for scraping surfaces, typically to remove residue, clean, or make the surface smoother, found in both household and industrial contexts.

Upper Paleolithic

The Upper Paleolithic is the third and last subdivision of the Paleolithic or Old Stone Age, characterized by the development of diverse and sophisticated tools, art, and cultural advances.

Pebble Tools

Primitive stone tools made by chipping small flakes from pebbles to create a sharp edge, used by early humans for cutting and scraping; typical of the Paleolithic era.