NSF North Mississippi GK-81 The Electromagnetic Spectrum Different wavelengths of EM waves. These...

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The Electromagnetic The Electromagnetic SpectrumSpectrum

• Different wavelengths of EM waves.

• These wavelengths

of light and others make up a spectrum.

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On the Spectrum…On the Spectrum…

Left Side Right Side

Type of Wave

Wavelength

Frequency

Energy

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VISIBLE LIGHT

Electromagnetic waves we can see.

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Visible Spectrum• The visible spectrum

contains seven colors.

• Each of these colors corresponds with a particular wavelength.– Longest wavelength=

red light– Shortest wavelength=

violet (purple) light

http://ldt.stanford.edu/ldt1999/Students/tita/mjrproj/color/wavereview.html

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How can I remember the seven colors of the visible

spectrum?

RROOYY GG BBIIVVED

RANGE

ELLOW

REEN

LUE

NDIGO

IOLET

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White LightWhite Light• White light is not a single color; it is

made up of a mixture of the seven colors of the rainbow.

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ColourWe can demonstrate this by splitting white light with a prism:

•This is how rainbows are formed: sunlight is “split up” by raindrops.

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Why do we see color?

• When our eyes see different wavelengths of light in the visible spectrum, we see colors.

http://www.astronomynotes.com/light/colorswvl.gif

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Seeing colour

– What we actually see is the light an object reflects or in some cases the light an object produces.

For example, a red book only reflects red light:

White

light

Only red light is

reflected

How do humans see color?

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Or…

• A red stoplight appears green because it produces red light.– It’s LUMINOUS!

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Seeing colour

– Absorption – the disappearance of an electromagnetic wave into a medium.• It’s the opposite of reflection!

White

light

Only red light is

reflected

The colors that don’t get reflected, are absorbed.

It absorbs all

the other

colors.

(OYGBIV)

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Sun’s R

ays (W

hite

Light)

Green Wavelength of

light

Absorbs all other colors

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A white hat would reflect all seven colors:

A pair of purple pants would reflect purple light

(and red and blue, as purple is made up of red and blue):

Purple light

White

light

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Using coloured light

• What about an outfit?

White

light

Shorts look blue

Shirt looks red

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Black

• When you see black, all of the wavelengths of light are absorbed and no light is reflected back at you.

White

light

Nothing is reflected.

All visible light is

absorbed.

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Moving on to the HUMAN EYE

• You will now become blind.– You have 5 minutes to

figure out how you are going to take halfway organized notes on the back of your Color Notes sheet.

– Remember: these notes will be used on the test! They need to be legible!

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The The Human Human

EyeEye

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HA! Even if you’re peeking, you can’t see

anything!