Math Problem Statement

Project Seafarer was an ambitious program to construct an enormous antenna, buried underground on a site about 10000 km2 in area. Its purpose was to transmit signals to submarines while they were deeply submerged. If the effective wavelength were 1.5 x 102 Earth radii, what would be the (a) frequency and (b) period of the radiation emitted? Ordinarily, electromagnetic radiations do not penetrate very far into conductors such as seawater. Take the Earth's radius to be 6370 km.

Solution

To calculate the frequency and period of the radiation emitted by Project Seafarer, we'll use the following relationships involving wavelength, frequency, and period:

  1. Speed of light (cc): Approximately 3.00×1083.00 \times 10^8 m/s.
  2. Wavelength (λ\lambda): Given as 1.5×1021.5 \times 10^2 Earth radii.

Step 1: Calculate the Wavelength

The Earth's radius is 63706370 km, so:

λ=1.5×102×6370 km\lambda = 1.5 \times 10^2 \times 6370 \text{ km} λ=1.5×100×6370 km=955500 km=955500×103 m=9.555×108 m\lambda = 1.5 \times 100 \times 6370 \text{ km} = 955500 \text{ km} = 955500 \times 10^3 \text{ m} = 9.555 \times 10^8 \text{ m}

Step 2: Calculate Frequency (ff)

Using the relationship:

f=cλf = \frac{c}{\lambda}

Substituting in the values:

f=3.00×108 m/s9.555×108 m0.314 Hzf = \frac{3.00 \times 10^8 \text{ m/s}}{9.555 \times 10^8 \text{ m}} \approx 0.314 \text{ Hz}

Step 3: Calculate Period (TT)

The period is the reciprocal of frequency:

T=1f=10.3143.18 sT = \frac{1}{f} = \frac{1}{0.314} \approx 3.18 \text{ s}

Summary of Results

(a) Frequency: f0.314 Hzf \approx 0.314 \text{ Hz}

(b) Period: T3.18 sT \approx 3.18 \text{ s}

If you have any questions or need further details, feel free to ask! Here are some related questions you might consider:

  1. What are the implications of this frequency for submarine communication?
  2. How does seawater's conductivity affect electromagnetic wave propagation?
  3. What other frequencies are typically used in submarine communication?
  4. How would the design of antennas change for different wavelengths?
  5. What are some practical challenges in constructing such a large antenna?

Tip: Always ensure that the wavelength used in calculations is in the correct unit (meters) for consistency with speed and frequency calculations.

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Math Problem Analysis

Mathematical Concepts

Wave Physics
Electromagnetic Waves
Frequency and Period Calculations

Formulas

Wavelength (λ) = 1.5 x 10^2 x Earth's radius
Frequency (f) = Speed of Light (c) / Wavelength (λ)
Period (T) = 1 / Frequency (f)

Theorems

Relationship between speed, wavelength, and frequency in wave equations

Suitable Grade Level

Grades 11-12