Physics Photo of the Week
At the first
of several large snowstorms this past winter, Warren Wilson's Tom
LaMuraglia operated the snowplow (front loader) to clear the roads
around campus. Thank you, Tom!
In several of the many large snow piles left by the snow clearing
machine, neighbor Tom Showalter noticed the definite blue color
within the cavities of the snowbank. This coloration of snow is a
real effect - not just an illusion or faulty color balance setting of
As light travels through snow, ice, or pure water, the light from the
red end of the visible spectrum is partially absorbed. If red is
removed from white light, the remaining light appears cyan or
"bluish". The greater the distance the light travels in the H20
greater the reduction of the red colors. Thus the
blue tint is more pronounced deep within the cavity in the snow bank.
The physical chemical reason for this light absorption lies in the
vibrations of the oxygen-hydrogen bond in the water molecules.
The oxygen-hydrogen bond will vibrate at a frequency corresponding to
infrared wavelength. However, the bond stretch in most
molecules is "non-linear", i. e. stretching more than twice as much
does not require twice the stretching force. As a result the bond
not only absorbs light at the natural vibrational frequency of the
bond, it also absorbs
light at overtones of the fundamental. These vibrational
overtones occur in the visible red - a higher frequency than the
infrared fundamental. If water is made by replacing the
hydrogen in H20 with deuterium, D20
the larger mass makes for a smaller vibration frequency, hence the
absorption of the light for D20, occurs further in the
infrared. As a result D20 does not show the blue
, J. Chem. Edu., 1993, 70(8)
, 612, summarized
at the web site:http://www.dartmouth.edu/~etrnsfer/water.htm).
Due to Spring Break at Warren Wilson College, there will be no Physics
Photo of the Week next week (March 19). The next Physics Photo of
the Week will be published on March 26, 2010.
Photo of the
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to firstname.lastname@example.org.
All photos and discussions are copyright by Donald
Collins or by the person credited for the photo and/or
discussion. These photos and discussions may be used for private
individual use or educational use. Any commercial use without
written permission of the photoprovider is forbidden.
the Physics Photo
the Week Archive.
Observers are invited to submit
digital photos to: