The Spectrum

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Slide 1

Light and Sound

To understand spectra you need a little primer on light first

It is helpful to think of light and sound together

They are both wave phenomena

Sound is a mechanical wave

Light is a electromagnetic wave

You can think of color as pitch and brightness as loudness

Slide 2

If the Rainbow was a Piano…

Red would be on the low side of the scale (bass) and violet would be on the high side (treble)

The range of colors is called the visible spectrum

What would be lower than low?

What would be higher than high?

Slide 3

A Low Note

Slide 4

A High Note

Slide 5

Here’s what all possible pitches together would sound like:

What would it look like?

Slide 6

Slide 7

That’s Right!

All possible colors added together with the same brightness make white

I know, you’re thinking “but if I mix all colors of paint together, it’s black.”

True, but paint doesn’t make light, it absorbs light. If paint absorbs all colors, what would you have?

Slide 8

Isaac Newton

Showed with a prism* that white light is a continuous band made of all colors

*How does a prism do this? I’ll explain the Physics after class if you wish.

Slide 9

Robert Boyle

A contemporary and adversary of Newton

Declared the prism to be the "usefullest Instrument" for gaining insight into the fleeting array of colors generated when sunlight passes through it.”

Slide 10

William Herschel

100 years after Boyle, Herschel viewed starlight through a prism

Saw differences in the width and intensity of the colors of the spectrum

Also detected “invisible rays”

Used a thermometer on each color and found “temperature” below red

Slide 11

Prisms

Featured on the best selling album of all time

Long before that, though, scientists were interested in improving on the design

One goal was to increase angular dispersion

Slide 12