Reflection and Refraction (Snell’s Law). Today’s agenda: Introduction to Light. You must develop a general understanding of what light is and how it behaves. Reflection and Refraction (Snell’s Law). You must be able to determine the path of light rays using the laws of reflection and refraction. Total Internal Reflection and Fiber Optics. You must be able to determine the conditions under which total internal reflection occurs, and apply total internal reflection to fiber optic and similar materials. Dispersion. You must understand that the index of refraction of a material is wavelength-dependent.

How many physicists does it take to change a light bulb? Normally, “light” refers to the type of electromagnetic wave that stimulates the retina of our eyes. Light acts like a wave except when it acts like particles. How many physicists does it take to change a light bulb?

Light—Waves or Particles?* http://www.nearingzero.net (quantum007.jpg) *Light is both! Take Physics 2305 for enlightenment!

The Speed of Light Light is a type of electromagnetic wave and travels with the speed c = 2.9979x108 m/s in a vacuum. (Just use 3x108!) How many physicists does it take to change a light bulb? Eleven. One to do it and ten to co-author the paper.

Visible light is a small part of the electromagnetic spectrum.

News Flash! Light slows down when it passes from a vacuum into matter! Details later!

Geometric Optics Although light is actually an electromagnetic wave, it generally travels in straight lines (like particles do!). We can describe many properties of light by assuming that it travels in straight-line paths in the form of rays. A ray is a straight line along which light is propagated. In other contexts, the definition of ray might be extended to include bent or curved lines. http://www.lab-initio.com (nz341.jpg)

thankfully, there really isn’t such a thing A light ray is an infinitely thin beam of light. Of course, there really isn’t such a thing, but the concept helps us visualize properties of light. thankfully, there really isn’t such a thing http://www.lab-initio.com (nz342.jpg)

*one zillion = 10a big number Light rays from some external source strike an object and reflect off it in all directions. We only see those light rays that reflect in the direction of our eyes. If you can see something, it must be a source of light! Zillions* of rays are simultaneously reflected in all directions from any point of an object. Later, when we study mirrors and lenses, we won’t try do draw them all! Just enough representative ones to understand what the light is doing. *one zillion = 10a big number