# Chapter 18: The Electromagnetic Spectrum and Light

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Chapter 18: The Electromagnetic Spectrum and Light
Section 3: The Behavior of Light Section 4: Color

The Behavior of Light You are only able to see objects if they reflect some light back to your eyes. All objects either absorb, reflect or transmit (let light pass through) light. Objects may interact with light in 3 ways: They can appear opaque They can appear translucent They can appear transparent

Opaque, Translucent and Transparent
Opaque materials only absorb or reflect light. No light passes through. Translucent materials allow some light to pass through (some light is also scattered) but things can not be viewed through them clearly. Transparent materials transmit almost all of the light that strikes them. Very little light is absorbed or reflected. This is a transparent canoe that is actually on the market for \$1, Hammacher Schlemmer

Reflection of Light Recall the Law of Reflection which states that the angle of incidence is equal to the angle of reflection. The smoother the surface of an object is, the surface tends to be more reflective. This is due to the fact that the rays of light are reflected in a regular pattern (regular reflection). Rough, uneven surfaces cause light to refract at different angles and irregular patterns that are very poor for reflecting an image (diffuse reflection).

Refraction of Light Recall that the speed of light is changed as it travels from one medium to another. How much light bends depends on the index of refraction. As the index of refraction increases, light is slowed down more. Devices like eyeglasses, binoculars, cameras and microscopes depend on refraction for imagery.

Prisms A prism is a triangular glass device that separated white light into the visible color spectrum. Isaac Newton was the first person to show how white light is made up of the visible spectrum. The prism causes refraction of light and will make the color bands red, orange, yellow, green, blue, indigo and violet visible.

Rainbows Water droplets reflect light just like miniature prisms.
This refraction of light allows us to observe rainbows in the sky as water molecules refract light. When white light is separated into colors it is called dispersion.

Colors – Light IN LIGHT:
Red, Blue and Green combine to form all of the colors of the visible spectrum. White is a combination of all colors of the light spectrum. Black is the reflection of almost no color.

Colors - Pigment IN PIGMENT (ART):
You are probably most familiar with pigment color mixtures. Magenta, Cyan and Yellow combine to form all of the pigment colors. White is the reflection of almost no color. Black is the reflection of a combination of all colors.

Lasers Lasers (light amplification by stimulated emission of radiation) are produced when photons are emitted as coherent light. Coherent light is when all of the waves in a light are have their crests and troughs the same and do not spread out far from the source beam. Lasers are used in scanners, as cutting tools and even as a way to transmit high speed information through optical fibers.