Chapter 16 :Fundamentals of Light Light is composed of an electric and magnetic component.

Ray Model of Light Light travels in straight lines until it encounters a boundary then it may be absorbed, refracted, or reflected. (..or some combination of those.) Objects, such as lights or the sun are called luminous sources, because they produce their own light.

Light and Matter There are 3 main types of matter when it comes to light passing through matter… Opaque objects do not pass light rays. Translucent objects pass images but not clear ones…light rays do not pass straight through. Transparent objects pass clear images, with no or slight light ray bending.

Quantity of Light The rate at which a luminous source produces light is called luminous flux. (P) The luminous flux falling on a given surface area at any instant is called illuminance. Illuminance is an inverse square relationship with distance…as distance increases, the illuminance decreases with the square of the distance.

Inverse Square of Illuminance

Luminous Intensity Luminous intensity is measured in units called candellas. Luminous intensity is luminous flux divided by 4π. If 2 sources have the same luminous intensity, a source at 2r would have ¼ the illuminance on a screen.

Surface Illumination

The Speed of Light The speed of light is constant in any given medium. We use c to represent the speed of light in a vacuum… c= 3.00x108 m/s The first person to measure light between any two spots was Danish astronomer Ole Roemer. Although many attempts were made of measuring the speed of light, Albert Michelson was the first to measure it with accuracy by measuring how long it took to travel between two mountains 35 km apart.

Problems With the Speed of Light C=fλ where c=3.00x108 m/s You should be able to do dimensional analysis with the speed of light…. How far does light travel in a week? 3.00x108m x 3600sec.x 24hr. X 7 days = 1.81x1014m/wk 1 sec 1hr. 1day 1 week