Physics Photo of the Week
April 9, 2009
Irridescent Turkey
This
handsome wild turkey lived in our neighborhood all winter. His
feathers show a shimmery irridescence when the lighting is right.
The irridiscence, or displaying many colors at once, is caused by the
diffraction of light by the fine structure in the feathers. Bird
feathers often show irridescence. To show the irridescence, the
feathers must contain structures (ridges, microhooks, etc) that are
regularly spaced and very close together (several hundred ridges per
mm). These features actually become a diffraction grating.
In certain directions the light of a particular color is reflected more
than light of other colors giving the appearance of a rainbow color
that changes with the angle.
Today's photo features the irridescence in the feathers of one of the
largest North American birds. Physics Photo of the Week featured
irridescence on one of the smallest North American birds - a
hummingbird - on PPOW
for April 25, 2008.
The photo at left is a close-up of the turkey's
wing feathers. Notice the almost metallic sheen to the
feathers. Also notice that some of the feathers in the upper left
(about 1/3 from the top left) are bluish while the feathers in te
center are golden. The bluish feathers will appear golden when
viewed face-on. The color that is reflected depends critically on
the angles of both the light and the viewing.
Compact
disks are a prime everyday example of diffraction. The thousands
of tiny pits or holes representing the information and tracks in the CD
diffract the light so that different colors are viewed from different
angles. Diffraction gratings are also very important
scientifically. They are used to separate light into spectra - an
important analytical tool for astronomy, physics, chemistry, and
biology.
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.
Click
here
to see the Physics Photo
of
the Week Archive.
Observers are invited to submit
digital photos to:
