1. The Electromagnetic Spectrum
Beyond the Spectrum of Visible Light
textbook 3.2, pp

2. The Electromagnetic Spectrum
Visible Light is only a small part of the possible frequencies for electromagnetic waves.
Milky Way Galaxy in visible light.

3. Frequency, Wavelength and Energy.
Radio Waves, X-rays, Infrared Rays etc. differ from visible light only in
Frequency, Wavelength and Energy.
Milky Way Galaxy in infrared light.

4. Infrared Radiation
In 1800, Sir William Hershel, who also discovered the planet Uranus, discovered that when he put a thermometer just off the red end of the visible spectrum, the thermometer registered an elevated temperature.
He concluded that some form of invisible energy existed as HEAT beyond the red end of the optical spectrum, and called it infrared.

6. Ultraviolet Light
In 1801, Johann Ritter noted that when he shined sunlight on a layer of silver chloride, the chemical blackened most strongly in the region just beyond the violet end of the spectrum.

7. Radio Waves
Radio waves were first predicted in the mid-1800s, and about 50 years later Karl Jansky discovered naturally occurring radio waves. Jansky also discovered that the center of the Milky Way Galaxy was a strong source of radio emission.

8. X -Rays
X-rays were detected coming from the Sun in the late 1940’s. X-ray waves are far shorter than those of visible light, typically between 0.01 and 10 nanometers.
X-Ray Milky Way Galaxy

9. Microwaves and Gamma Rays
Microwaves and gamma rays are strongly blocked by the Earth’s atmosphere, and are the most difficult to observe.
Microwave Milky Way Galaxy