Why the sky changes colour

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Slide 11

We Must First Understand…

[The other half of] Why sky is blue.

Slide 12

Blue Sky

When Sun is high in the sky, it emits wavelengths at the shortest angle

What colour does the shortest angle allow for…?

Slide 13

Blue Sky (Part 2)

Blue light is the shortest distance in atmosphere

Atmospheric gases absorb blue and violet colours and cause them to scatter (more than any other colour)

Rayleigh scattering

Human eyes do not register violet well

…and so humans see blue!

Slide 14

Atmosphere – Video

http://www.discovery.ca/things/default.htm?clipid=510962

[0:56 – 1:34 min]

Slide 15

Blue never goes away… we just cannot see it sometimes!

Slide 16

And finally…

Sunrise and Sunset

Slide 17

Sunrise

When Sun reaches Earth, there is a longer angle

What colours does the longest angle allow for…?

As Sun gets higher in sky, these colours fade and blue light becomes more scattered

Blue sky returns

Slide 18

Sunset

Reverse sunrise… but a bolder display

Dust/debris is being kicked around during the day

This filters light

Polluted cities have the most beautiful sunsets

Slide 19

How are the Details Determined?

Slide 20

Details

Dust

Pollution

Smog

Clouds

Water vapour or humidity causes the sky to appear gray because it deflects light

Slide 21

The End!

Slide 22

Works Cited

Adams, Julia. "What Makes the Sky Change Colours?" Colours. N.p., n.d. Web. 8 Dec. 2013.

<http://www.sewanee.edu/chem/Chem&A

"Color." The Physics Hypertextbook. N.p., n.d. Web. 9 Dec. 2013. <http://physics.info/color/>.

Corfidi, Stephen F "The Colors of Sunset and Twilight." THE COLORS OF TWILIGHT AND SUNSET. N.p., n.d. Web. 18 Dec.

2013. <http://www.spc.noaa.gov/publications/corfidi/sunset/