Physics 125

Course Description Course Details Related Fun Stuff

This web site is http://www-unix.oit.umass.edu/~phys125/

This page is almost always under construction.
Please pardon our mess.

Instructor:

Prof. Guy Blaylock

Office:

Lederle Grad Research Tower Rm 1034

Phone:

(413) 545-0993

blaylock@physics.umass.edu

Office hours:

MW 10-11am and by appointment

Course Description

Seeing the Light is an introductory course on light and vision intended for anyone with an interest in the physical and natural worlds around them. The course covers a wide range of subjects including basic optics, photography, light in nature, visual anatomy, visual perception, and many topics in modern technology. A complete survey of basic optics is presented, including the tools necessary to understand most optical instruments (telescopes, microscopes, cameras). An introduction to photography provides an important application of concepts in basic optics. A section on light in nature teaches students how shadows behave, how mirages work, what a green flash is, why the sky is blue, why the sunset is red, and how a rainbow works. A detailed section on anatomy of the human eye provides the basis for understanding many interesting features of human vision. Visual perception, particularly depth and color perception, is covered using many examples from art. The course introduces the standard model of color and the features of human vision that lead to optical illusions. Connections to modern technology appear throughout the course in the discussion of light fibers, telecommunications, coated optics, polarizing lenses, retroreflectors, diffraction gratings and lasers. The course is designed for an audience with competence in basic algebra and geometry and is taught with a strong emphasis on demonstration and experimental observation. It is three-credits and statisfies the general education physical sciences requirement. Lectures are three hours per week, with weekly graded problem sets. An additional one-hour small group discussion section is optional as a one-credit honors supplement (Physics H01 course number 192017).

Course details

Course components, including lectures, discussion and help sessions, homework and exams.
Text: "Seeing the Light" by Falk, Brill and Stork, John Wiley and Sons, Inc. (1986).
For interested students, a selection of materials is on reserve in the Physical Science Library.
Grading Policy
Detailed syllabus with reading assignments.

Other Related Websites

What distinguishes shadows from a point light source and shadows from an extended light source? The first homework set in this course tries to teach you about the umbra and penumbra of shadows, and their role in eclipses and phases of the moon. Here is a link to a java demo that demonstrates shadows from point and extended light sources. It's useful for checking one of the problems in your first homework set. The image at the left is a link to a web site showing the phases of the moon, updated every 4 hours. Useful for figuring what phase of the moon you were born under.

A solar eclipse occurs when the moon comes between the earth and the sun. Not all solar eclipses completely block out the sunlight. A partial eclipse is visible when the earth passes through the moon's penumbra at the side of the shadow. An annular eclipse occurs when the earth passes through the center of the shadow but beyond the reach of the umbra. The image at the left is a link to a real video archive of two total solar eclipses from Feb 26, 98 and Aug 11, 99.

The physics of rainbows was first correctly explained in a treatise by Rene Descartes in 1637. In that treatise he carefully traced light rays through a spherical drop of water to determine how the different colors are dispersed. The linked image at the left will take you to a site with a Java demo of ray tracing through a spherical waterdrop. There you can adjust the incident light rays to understand how different rays behave and how they contribute to the pattern of light that emerges.
Note: If you are interested in further study about light in nature, you may wish to check out Robert Greenler's book on reserve in the physical science library, or Tom Arny's astronomy 105 course on weather. Prof. Arny's course covers some of the topics we discuss in our classroom, including halos, mirages, and glories.

Part of this course involves the study of introductory optics and how light rays refract and reflect off of lenses and mirrors. The basic tool for understanding these phenomena is called "ray tracing", a technique for following light rays through lenses or mirrors to calculate the location, orientation and size of images. The picture at the left links to a very nice java demo for ray tracing. It is quite useful for checking many of the homework problems in introductory optics.

"The Exploratorium", located just south of the Golden Gate in San Francisco, is probably the best hands-on science museum in the world. It contains a football-field-sized warehouse of interactive science exhibits. It's www pages describe many of the exhibits as well as a large catalog of other useful information. The section on science snacks, geared largely to the younger crowd, explains a number of everyday scientific phenomena and provides some small version of exploratorium exhibits one can perform at home. The snack called "real image" explains the parabolic mirror illusion we have used in class and describes how to make your own version out of a Christmas tree ornament.

In its simplest incarnation, the telescope is merely a pair of lenses or a mirror and a lens for viewing distant objects. However, modern day research telescopes can be far more sophisticated and the results far more impressive than what Galileo first used to view the moons of Jupiter. The image at the left is the deep field view from the "Hubble space telescope". Only a few dots of light in that photo are stars, the rest are galaxies. Clicking on the image will take you to a larger version suitable for viewing. The following "link" takes you to an enlargment of a portion of the deep field showing one of the most distant galaxies observed by man (arrow).

Although very impressive, Hubble is by no means the biggest optical scope around. That distinction is reserved for the twin Keck telescopes on top of Mauna Kea in Hawaii. The image link at the left takes you the Keck home page where you can read about the construction of these amazing instruments, and see some of the images captured by their 10 meter diameter mirrors.

Random dot stereograms, such as the image at the left, can produce the appearance of depth when viewed in the right way. They operate by providing a repeating pattern of dots that can confuse the brain into thinking it is seeing only one pattern. Many different patterns will produce this effect, including many wallpapers. Here is a link to a simple ascii stereogram that may give you a clue as to how they work. For a more sophisticated random dot stereogram, click on the image at the left to see a larger version suitable for viewing. Many more stereogram images can be found elsewhere on the web. Try this link for a centralized list of many web pages on stereograms. Additionally, this link takes you to a good FAQ web site on stereograms that explains many of the features of stereograms.

Optical illusions such as M. C. Escher's impossible waterfall at the left often use features of human visual perception to lead the brain to a logical inconsistency. Click on the image to jump to a web site that specializes in optical illusions, with tutorials and many wonderful examples.

The wave model for light is an indispensible tool for understanding the bizarre features of diffraction (spreading and bending of light around corners) and interference (cancellation of light). Fortunately, the wave model also allows us to explain the features of light that we previously understood from wave optics, namely reflection and refraction. The portrait of Christiaan Huygens at the left links to a Java demo that uses Huygens' principle of wave propagation to demonstrate reflection and refraction of waves. By adjusting the parameters of the demo, you can see how a series of point sources that make up a plane wave reproduces the law of reflection and Snell's law of refraction.

Last updated November 27, 2001

Instructor:	Prof. Guy Blaylock
Office:	Lederle Grad Research Tower Rm 1034
Phone:	(413) 545-0993
	blaylock@physics.umass.edu
Office hours:	MW 10-11am and by appointment

	What distinguishes shadows from a point light source and shadows from an extended light source? The first homework set in this course tries to teach you about the umbra and penumbra of shadows, and their role in eclipses and phases of the moon. Here is a link to a java demo that demonstrates shadows from point and extended light sources. It's useful for checking one of the problems in your first homework set. The image at the left is a link to a web site showing the phases of the moon, updated every 4 hours. Useful for figuring what phase of the moon you were born under.
	A solar eclipse occurs when the moon comes between the earth and the sun. Not all solar eclipses completely block out the sunlight. A partial eclipse is visible when the earth passes through the moon's penumbra at the side of the shadow. An annular eclipse occurs when the earth passes through the center of the shadow but beyond the reach of the umbra. The image at the left is a link to a real video archive of two total solar eclipses from Feb 26, 98 and Aug 11, 99.
	The physics of rainbows was first correctly explained in a treatise by Rene Descartes in 1637. In that treatise he carefully traced light rays through a spherical drop of water to determine how the different colors are dispersed. The linked image at the left will take you to a site with a Java demo of ray tracing through a spherical waterdrop. There you can adjust the incident light rays to understand how different rays behave and how they contribute to the pattern of light that emerges. Note: If you are interested in further study about light in nature, you may wish to check out Robert Greenler's book on reserve in the physical science library, or Tom Arny's astronomy 105 course on weather. Prof. Arny's course covers some of the topics we discuss in our classroom, including halos, mirages, and glories.
	Part of this course involves the study of introductory optics and how light rays refract and reflect off of lenses and mirrors. The basic tool for understanding these phenomena is called "ray tracing", a technique for following light rays through lenses or mirrors to calculate the location, orientation and size of images. The picture at the left links to a very nice java demo for ray tracing. It is quite useful for checking many of the homework problems in introductory optics.
	"The Exploratorium", located just south of the Golden Gate in San Francisco, is probably the best hands-on science museum in the world. It contains a football-field-sized warehouse of interactive science exhibits. It's www pages describe many of the exhibits as well as a large catalog of other useful information. The section on science snacks, geared largely to the younger crowd, explains a number of everyday scientific phenomena and provides some small version of exploratorium exhibits one can perform at home. The snack called "real image" explains the parabolic mirror illusion we have used in class and describes how to make your own version out of a Christmas tree ornament.
	In its simplest incarnation, the telescope is merely a pair of lenses or a mirror and a lens for viewing distant objects. However, modern day research telescopes can be far more sophisticated and the results far more impressive than what Galileo first used to view the moons of Jupiter. The image at the left is the deep field view from the "Hubble space telescope". Only a few dots of light in that photo are stars, the rest are galaxies. Clicking on the image will take you to a larger version suitable for viewing. The following "link" takes you to an enlargment of a portion of the deep field showing one of the most distant galaxies observed by man (arrow).
	Although very impressive, Hubble is by no means the biggest optical scope around. That distinction is reserved for the twin Keck telescopes on top of Mauna Kea in Hawaii. The image link at the left takes you the Keck home page where you can read about the construction of these amazing instruments, and see some of the images captured by their 10 meter diameter mirrors.
	Random dot stereograms, such as the image at the left, can produce the appearance of depth when viewed in the right way. They operate by providing a repeating pattern of dots that can confuse the brain into thinking it is seeing only one pattern. Many different patterns will produce this effect, including many wallpapers. Here is a link to a simple ascii stereogram that may give you a clue as to how they work. For a more sophisticated random dot stereogram, click on the image at the left to see a larger version suitable for viewing. Many more stereogram images can be found elsewhere on the web. Try this link for a centralized list of many web pages on stereograms. Additionally, this link takes you to a good FAQ web site on stereograms that explains many of the features of stereograms.
	Optical illusions such as M. C. Escher's impossible waterfall at the left often use features of human visual perception to lead the brain to a logical inconsistency. Click on the image to jump to a web site that specializes in optical illusions, with tutorials and many wonderful examples.
	The wave model for light is an indispensible tool for understanding the bizarre features of diffraction (spreading and bending of light around corners) and interference (cancellation of light). Fortunately, the wave model also allows us to explain the features of light that we previously understood from wave optics, namely reflection and refraction. The portrait of Christiaan Huygens at the left links to a Java demo that uses Huygens' principle of wave propagation to demonstrate reflection and refraction of waves. By adjusting the parameters of the demo, you can see how a series of point sources that make up a plane wave reproduces the law of reflection and Snell's law of refraction.