16.3 Photons and Atoms 1

Chapter 16 Objectives Describe at least five properties of light. Describe the meaning of the term “intensity.” Use the speed of light to calculate the time or distance traveled by light. Explain how we perceive color in terms of the three primary colors. Explain the difference between the additive and subtractive color processes. Arrange the colors of light in order of increasing energy, starting with red. Describe light in terms of photons, energy, and color. 2

Chapter 16 Vocabulary Terms additive process black blue CMYK color process color cone cell cyan fluorescence green incandescence infrared intensity inverse square law light ray magenta photoluminescence photon photoreceptor pixel red RGB color model rod cell speed of light spherical pattern subtractive process ultraviolet white light yellow

Inv 16.3 Photons and Atoms Investigation Key Question: How does light fit into the atomic theory of matter? 4

16.2 Photons and atoms Just like matter is made of tiny particles called atoms, light energy comes in tiny bundles called photons. White light is a mixture of photons with a wide range of colors (energies). For a given temperature, the atoms in a material have a range of energy that goes from zero up to a maximum that depends on the temperature.

15.2 White light White light is a mixture of photons with a wide range of colors or energies. The number of atoms with a given amount of energy depends on the temperature.

16.2 Photons and intensity Intensity measures power per unit area. There are two ways to make light of high intensity. One way is to have high- energy photons. A second way is to have a lot of photons even if they are low-energy. The number and energy of photons determine the intensity of the light.

16.2 Photons and intensity The light from the flashlight cannot energize phosphorus atoms that your hand blocks. These atoms will not glow because they did not receive any energy from photons from the flashlight. The explanation is that each phosphorus atom absorbs (or emits) only one photon at a time.

16.3 Light and atoms Almost all atoms absorb and emit light. For most atoms, the absorption and emission of light happens in less than one-millionth of a second.

Color Printing Modern printing presses use the four-color, CMYK process to produce rich, vivid colors from only four inks. Careful alignment of the printing stations ensures that the dots line up and do not overlap each other.