Hands-on Science at Pasadena Public Library

Inspired by Young Readers League selection, Circus

Mirandus by Cassie Beasley

Be A Light Bender

November 18, 2016

First, a question:

WHY IS THE SKY BLUE?

Let’s probe further with an opposite

question:

WHY IS THE sun red at

sunset?

Both have to do with the scattering of light

through Earth’s atmosphere…

“The sky is blue because blue light is most readily scattered from sunlight in our atmosphere… If blue light was not scattered in the atmosphere, the sun would look a little less yellow and a little more white, and the sky would not be blue.”https://www.exploratorium.edu/snacks/glue-stick-sunsetCredit: www.pingry.orghttps://astrobob.areavoices.com/2012/08/26/what-color-is-the-sun/

“At sunset the sun is low—near the horizon—and light travels through a greater thickness of atmosphere before reaching your eyes than it does when the sun is higher in the sky… [T]he sunset appears red when the atmospheric path through which the sunlight travels gets longer. ”

https://www.exploratorium.edu/snacks/glue-stick-sunset

Illustration: Bob King https://astrobob.areavoices.com/2012/08/26/what-color-is-the-sun/

Now that we’ve seen how a beam of sunlight changes color as it travels through

the atmosphere at different angles and different

densities, let’s ask another question:

WHAT COLOR IS our sun?

Answer:

White(with a hint

of yellow)

“If you could travel into space and look at the Sun without going blind, you’d find that it’s actually

white, and not yellow… Our Sun appears yellow to us because of the atmosphere.”

http://www.universetoday.com/18689/color-of-the-sun/

A white sun in airless, black outer space seen from the International Space Station. Credit: NASAhttps://astrobob.areavoices.com/2012/08/26/what-color-is-the-sun/

Let’s ask another question!

WHAT is our sun made

of?

http://alexpetty.com/2014/09/21/the-periodic-table-of-light/

https://www.britannica.com/topic/Fraunhofer-lines

Turn off lights

Spectroscope Findings

http://blog.sdss.org/tag/spectroscope/

Spectroscope Findings

http://www.scienceinschool.org/2007/issue4/spectrometer

Additive Mixtures“When lights of different colors shine on the same spot on a white surface, the light reflecting from that spot to your eyes is called an additive mixture because it is the sum of all the light. We can learn about human color perception by using colored lights to make additive color mixtures.”

https://www.exploratorium.edu/snacks/colored-shadows

Additive Mixtures“With these three lights you can make shadows of seven different colors—blue, red, green, black, cyan, magenta, and yellow—by blocking different combinations of lights… When you block two lights, you see a shadow of the third color—for example, block the red and green lights and you get a blue shadow. If you block only one of the lights, you get a shadow whose color is a mixture of the other two. Block the red light and the blue and green light mix to create cyan; block the green light and the red and blue light make magenta; block the blue light and red and green make yellow. If you block all three lights, you get a black shadow.”

https://www.exploratorium.edu/snacks/colored-shadows

Color Filters

https://www.exploratorium.edu/snacks/color-table

What’s going on?

write a secret

message!

CMYKCMYK is a color system used by printers for making most* of the colors of the rainbow with just four basic colors: Cyan, Magenta, Yellow and BlacK. Almost all the graphic novels you read are printed in CMYK! *CMYK makes fewer colors than RGB and many other color systems, but has been around longerReferences:The Complete Idiot's Guide to Creating a Graphic Novel, 2nd Edition By Nat Gertler, Steve Lieberhttps://graphiccommunicationsworkshop.wordpress.com/2011/10/21/week-8-prepress/http://www.tucsononcanvas.com/include/guide_color_space_rgb_cmyk.php https://negliadesign.com/ask-a-designer/whats-the-difference-between-pms-cmyk-rgb-and-hex/

Make your own cymk rainbow!

Inverse Square LawLight intensity follows

an inverse square law, that the light spreads out and becomes less intense according to the square of the distance. This is why it gets dimmer and dimmer the farther you get from the source.

https://en.wikipedia.org/wiki/Inverse-square_law#Example

Prove it…Okay! With some graph paper, a light source, and a card with a square hole, we can actually test the math of this

equation.

https://en.wikipedia.org/wiki/Inverse-square_law#Examplehttps://www.exploratorium.edu/snacks/inverse-square-law

Want to read more about light?

Check out these great books from Pasadena Public Library:

Thanks for coming! Be sure to read Circus Mirandus by Cassie Beasley, and come to

our Circus Extravagaza tomorrow at 2 pm.

Stay curious!