Department of Physics and Astronomy, University of Rochester, Slide 15
Einstein's Theories:
The photoelectric effect.
¥Experiments showed that
light can liberate electrons from a material (the photoelectrons).
¥The following surprising
observations were made:
¥No
electrons are liberated if the wavelength of the light is larger than some
critical value (independent of the intensity of the light).
¥The
maximum energy of the electrons liberated does not depend on the intensity of
the light. It only depends on the
wavelength of the incident light.
http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html
http://www.mhhe.com/physsci/astronomy/fix/student/chapter6/06f07.html