What is this?
The electromagnetic spectrum
What does Hz represent?
Hertz, a unit of frequency. 1 Hz = 1 cycle/second. This sometimes just written as sec-1.
What does m and nm represent?
meters and nanometers. A nanometer is 10-9 meter, or 1 billionth of a meter.
What kind of scale is the frequency scale in this diagram?
Logarithmic. Even though the tick marks are evenly spaced, they go up by a factor of 100.
What is the relationship between energy, frequency, and wavelength?
Energy increases with frequency.
Frequency and wavelength are inversely proportional to each other.
Therefore, energy goes down as wavelength increases.
What are the parts of the electromagnetic spectrum in order from lowest energy to highest energy?
- Radio waves
- Microwaves
- Infrared
- Light
- Ultraviolet
- Xrays
- Gamma rays
Why is the spectrum divided into different types of waves?
Electromagnetic waves are categorized based on how they interact with matter, typically by how they are produced or how they are detected.
| Type of EM wave | Interaction |
| Radio waves | Produced by an antenna |
| Microwaves | Produced by magnetron, absorbed by water |
| Infrared | Produced by the motion of atoms, heat objects that absorb them |
| Light waves | Produced by electrons changing orbitals, detected by our eyes |
| Ultraviolet | Has enough energy to break chemical bonds |
| X-rays | Produced by rapid deceleration of electrons, penetrates through human body |
| Gamma rays | Produced in nuclear reactions |
There is some overlap between these categories. For instance, microwaves are sometimes considered a subset of radio waves. The same wave might be classified as an x-ray or a gamma ray, depending on how it is produced.
What is the difference between sound waves and electromagnetic waves?
Sound waves are due to the motion of particles in the air, whereas electromagnetic waves are due to the changing electromagnetic field.
Even though sound waves have a frequency, they do not belong on the electromagnetic spectrum.
CoMo Science 
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