Interference by thin films
- Light which partially passes through and partially reflects off
a thin film of material can interfere with itself
- If a light ray in one substance reflects off an interface
to a material with a higher index of refraction, its phase is
- If a ray which reflects off the front surface a film, and a ray
which reflects off the back surface of a film, recombine in
phase, one sees the reflected light; if they recombine out of phase,
no reflection appears
- The reflection from a thin film can depend strongly on wavelength
Have you ever looked at a spot in a parking lot where oil
dripping from a leaky car has created a shallow puddle?
This image of an oil slick is Copyright 2005 Jeff Wignall,
and is reproduced from
an Instructor Insights column on betterphoto.com
Have you ever noticed the intense colors of a butterfly's
Creative Commons .
These are examples of iridescence,
the color produced when sunlight strikes
a very thin film of material.