http://www.ck12.org Chapter 21. Electromagnetic Radiation
Therefore, if either wavelength or frequency is known, the missing value can be calculated. Consider an electromag-
netic wave that has a wavelength of 3 meters. Its speed, like the speed of all electromagnetic waves, is 3.0× 108
meters per second. Its frequency can be found by substituting these values into the frequency equation:
Frequency=
3. 0 × 108 m/s
3 .0 m= 1. 0 × 108 waves/s, or 1. 0 × 108 hertz (Hz)You Try It!
Problem:What is the wavelength of an electromagnetic wave that has a frequency of 3.0× 108 hertz?
For more practice calculating the frequency and wavelength of electromagnetic waves, go to these URLs:
Lesson Summary
- All electromagnetic waves travel at the same speed through space, called the speed of light, which equals 3.0
× 108 meters per second. Electromagnetic waves travel more slowly through a medium. - Electromagnetic waves differ in their wavelengths and frequencies. The higher the frequency of an electro-
magnetic wave, the greater its energy. The speed of an electromagnetic wave is the product of its wavelength
and frequency, so a wave with a shorter wavelength has a higher frequency, and vice versa.
Lesson Review Questions
Recall
- What is the speed of light?
- What is the wavelength of an electromagnetic wave?
- Describe the range of frequencies of electromagnetic waves.
Apply Concepts
- If an electromagnetic wave has a wavelength of 1 meter, what is its frequency?
Think Critically
- Explain why light waves bend when they pass from air to water at an angle.
- Explain the relationship between frequency and wavelength of electromagnetic waves.
Points to Consider
In this lesson, you learned that electromagnetic waves vary in their wavelength and frequency. The complete range
of wavelengths and frequencies of electromagnetic waves is outlined in the next lesson, "The Electromagnetic