This document provides explanations for common science questions about light and color. It discusses why the sky is blue and the sun appears red at sunset, which is due to scattering of light in the atmosphere. The document also notes that the sun appears white in space and is made mostly of hydrogen and helium. It introduces the concepts of additive color mixing using colored lights and subtractive color mixing using CMYK pigments. Finally, it explains the inverse square law for light intensity over distance.

1. Hands-on Science at Pasadena
Public Library
Inspired by Young Readers
League selection, Circus
Mirandus by Cassie Beasley
November 18, 2016

2. WHY IS THE SKY
BLUE?

3. WHY IS THE sun red at
sunset?

4. “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-sunset
Credit: www.pingry.org
https://astrobob.areavoices.com/2012/08/26/what-color-is-the-
sun/

5. “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/

6. WHAT COLOR IS our
sun?

7. White
(with a hint of yellow)
A white sun in airless, black outer space seen from the International Space Station. Credit: NASA
https://astrobob.areavoices.com/2012/08/26/what-color-is-the-sun/

8. WHAT is our sun made
of?

9. http://alexpetty.com/2014/09/21/the-periodic-table-of-light/
https://www.britannica.com/topic/Fraunhofer-lines

10. Turn off lights

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

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

13. “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.ed
u/snacks/colored-shadows

14. “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.ed
u/snacks/colored-shadows

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

19. write a secret message!

20. CMYK 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 longer
References:
The Complete Idiot's Guide to Creating a Graphic Novel, 2nd Edition By Nat Gertler, Steve Lieber
https://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/

24. Make your own cymk
rainbow!

25. Light 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

26. 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#Example
https://www.exploratorium.edu/snacks/inverse-square-law