Electromagnetic Waves Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Electromagnetic Waves.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

Transverse waves consisting of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of propagation.

Light, radio, X-rays—all are EM waves, just different frequencies.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: EM waves don't need a medium—they can travel through empty space.

Common stuck point: All EM waves travel at the speed of light in vacuum, regardless of frequency.

Sense of Study hint: When solving an EM wave problem, remember that all electromagnetic waves travel at c = 3 \times 10^8 m/s in vacuum. Use c = f\lambda to convert between frequency and wavelength. To find photon energy, use E = hf. Identify which part of the EM spectrum the wave belongs to based on its frequency or wavelength.

Worked Examples

Example 1

easy
An electromagnetic wave has a frequency of 6 \times 10^{14} \text{ Hz}. What is its wavelength? What type of EM radiation is this? Use c = 3 \times 10^8 \text{ m/s}.

Solution

  1. 1
    All EM waves travel at the speed of light: \lambda = \frac{c}{f}.
  2. 2
    \lambda = \frac{3 \times 10^8}{6 \times 10^{14}} = 5 \times 10^{-7} \text{ m} = 500 \text{ nm}
  3. 3
    This is in the visible light range, corresponding to blue-green light.

Answer

\lambda = 500 \text{ nm (visible light, blue-green)}
Electromagnetic waves are oscillating electric and magnetic fields that travel at the speed of light. They do not require a medium and can travel through a vacuum.

Example 2

medium
How long does it take light from the Sun to reach Earth? The Sun-Earth distance is 1.5 \times 10^{11} \text{ m} and c = 3 \times 10^8 \text{ m/s}.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
A microwave oven operates at a frequency of 2.45 \times 10^9 \text{ Hz}. What is the wavelength of the microwaves? Use c = 3 \times 10^8 \text{ m/s}.

Example 2

hard
A WiFi router transmits at 5 \text{ GHz} with a power of 0.1 \text{ W}. What is the wavelength? If the signal spreads uniformly in all directions, what is the intensity at 10 \text{ m}? Use c = 3 \times 10^8 \text{ m/s}.
← Back to Electromagnetic Waves Practice Mode

Background Knowledge

These ideas may be useful before you work through the harder examples.

wavestransverse wave