Diffraction Physics Example 3

Follow the full solution, then compare it with the other examples linked below.

Example 3

medium
Visible light (λ≈500 nm\lambda \approx 500 \text{ nm}) and radio waves (λ≈1 m\lambda \approx 1 \text{ m}) both encounter a building 10 m10 \text{ m} wide. Which wave diffracts more around the building? Why?

Solution

  1. 1
    Diffraction is significant when λ\lambda is comparable to the obstacle size.
  2. 2
    Radio waves (λ=1 m\lambda = 1 \text{ m}) compared to building (10 m10 \text{ m}): ratio λd=0.1\frac{\lambda}{d} = 0.1 — moderate diffraction.
  3. 3
    Light (λ=500 nm=5×10−7 m\lambda = 500 \text{ nm} = 5 \times 10^{-7} \text{ m}) compared to building: ratio λd=5×10−8\frac{\lambda}{d} = 5 \times 10^{-8} — negligible diffraction. Radio waves diffract much more.

Answer

Radio waves diffract significantly more around the building.\text{Radio waves diffract significantly more around the building.}
Radio waves have wavelengths comparable to everyday obstacles, so they diffract around buildings and hills. Visible light has extremely short wavelengths relative to most objects, so it travels in nearly straight lines.

About Diffraction

The spreading of a wave as it passes through a gap or around the edge of an obstacle.

Learn more about Diffraction →

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