Physics Photo of the
Week
August 26, 2011
Crepuscular Rays - Dawn of a New Day
This magnificent sunrise on August 17, 2011 is
enhanced by the crepuscular rays, a fan-like pattern emanating
from the Sun's position. The Sun normally lights the
sky, but the intermittent clouds cast shadows into the
sky. The fan-like appearance of the shadow bands is
simply an illusion. Because the Sun is a great distance
from the Earth, the shadow bands are actually parallel.
The apparent convergence of the paralel rays is analogous to
the apparent convergence of parallel railroad tracks in a
perspective view (see
a good student discussion on PPOW for Dec. 15, 2006).
In this case these rays are not only parallel, but they are
also horizontal because the Sun is actually on the
horizon. The true horizon is a bit difficult to
determine in the mountains, however
Physics Photo of the Week
is 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 dcollins@warren-wilson.edu.
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.
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here
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