A History LessonThe year was 1802, and William Wollaston was looking at the sun.

Through a pinhole. And a prism.

The pinhole made it so he could actually look into the spectrum without his retina burning in the suns glory.

HE OBSERVED dark lines....ominous.

He thought he saw the natural Boundaries of the colors.

A Generation goes by...

Now the year was 1814, and Joseph Fraunhofer was doing the same thing...

With more sophisticated equipment.

And he saw EVEN MORE dark lines. Too many to be color boundaries...

Later on

In 1836 David Brewster passed light (from a hot glowing object) through a diffuse gas (nitrous oxide), and THEN through a prism.

When there was NO GAS the spectrum was continuous, no lines

With the GAS there were mysterious dark lines.

So maybe the sun has layers of diffuse gas, absorbing some of the colors of the spectrum,and making dark lines.

Previously

in 1800 Herschel found that different amounts of heat passed more easily through different colored filters

Leading him to place a thermometer (cutting edge technology) into the spectrum.In the Violet end of the spectrum, there is practically no reading.And things heat up gradually,Until the Red end of the spectrum, where the reading is highest...

but not.Because if you move the thermometre even further PAST the red, youll find an even GREATER TEMPERATURE D:

THUS WAS BORN HUMAN KNOWLEDGE OF INFRARED RADIATION

a year later

Johann Ritter, knowing Herchels research, and knowing that violet light tends to darken silver chloride, thought to place silver chloride further than violet in the spectrum

and the crystals darkened FASTER

THUS WAS BORN HUMAN KNOWLEDGE OF ULTRAVIOLET RADIATION

Much later, silver chloride made into a slurry and applied to paper made the beginnings of photography.

FrequenciesFM radio measured in 10^8 HzVisible light, around 10^14 Hz

So far, two types of spectrum. Continuous, as in hot fire poker, or incadescent lightbulb, and Absorption spectrum, as when the light passed through a diffuse gas first, absorbing colors.

THERE IS A THIRD TYPE, called an emmision spectrum, created when a gas is heated, such as Neon or Mercury vapour.

This type of spectrum contains only a few colors.