# Chapter 25: Light Are you color coordinated? California Standards 4.Waves have characteristic properties that do not depend on the type of wave. As a.

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Chapter 25: Light Are you color coordinated?

California Standards 4.Waves have characteristic properties that do not depend on the type of wave. As a basis for understanding this concept: 4c. Students know how to solve problems involving wavelength, frequency, and wave speed. 4e. Students know radio waves, light, and X-rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in a vacuum is approximately 3×10 8 m/s (186,000 miles/second).

25.1 Light Fundamentals

25.1 Objectives Describe the ray model of light. Recognize that light is the visible portion of an entire range of electromagnetic frequencies. Solve problems involving the speed of light. Define luminous intensity, luminous flux, and illuminance. Solve illumination problems.

What is Light? What is light? Light is a form of energy. Light is the range of frequencies of electromagnetic waves that stimulates the retina of the eye. Light has wavelengths from about 400 nm (4.00 x 10 -7 m) to 700 nm (7.00 x 10 -7 m). Light behaves like both a particle and a wave.

What is Light?

Light Frequencies The electromagnetic wave spectrum covers Radio, microwaves, infrared (IR), ultraviolet (UV), X-rays, Gamma Rays, and visible light. Visible light is a very small portion of the entire scale.

Light Frequencies It is now known that the ranges of X-rays and Gamma Rays largely overlap. X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus. All EM waves produce photon particles.

The Speed of Light Light travels at the speed of 299,792,458 m/s. We use 3x10 8 m/s most commonly for calculations. The colors start at purple, and move to blue, green, yellow, orange, and red as the wavelength is increased. This is how fast light travels from the sun to the earth (8 min 18 sec).

The Ray Model of Light

The ray model is a generic one. By using it we can discuss the path taken by the light, without committing ourselves to any specific description of what it is that is moving along that path. We will use the nice simple ray model for most of this book, and with it we can analyze a great many devices and phenomena.

Illumination Luminance: Candela per square meter (cd/m 2 ) Luminous Intensity: Candela (lm/sr; lumen/steradian) Luminous Flux: Lumen (lm=cd  sr; candela × steradian) Illuminance: Lux (lm/m 2 )

Illumination Luminous Flux: Lumen (lm=cd  sr; candela × steradian).

Brightness

Materials and Light Opaque: No incident light is transmitted. Transparent: Transmits incident light WITHOUT distortion. Translucent: Transmits incident light WITH distortion.

Materials and Light Opaque, Transparent, or Translucent?

Light and Transparent Materials

Optical Illusions

Rainbows

Why is the Sky Blue & Sunset Pink?

25.2 Light and Matter

25.2 Objectives Explain the formation of color by light and by pigments or dyes. Explain the cause and give examples of interference in thin films. Describe methods of producing polarized light.

Prisms can be used to diffract light into all the colors of the spectrum.

Mixing Colors Why do the colors on the left combine to white and those on the right combine to black?

Primary and Secondary Colors Primary Color: Red, Green, Blue Secondary Color: Colors formed from an YellowCyan two primary colors: Yellow, Cyan, Magenta Primary Pigment: Absorbs ONE primary color. Secondary Pigment: Absorbs TWO primary colors.

Mixing Colors

M MMRYYGGCCBMMMMRYYGGCCBMMYGCM Mr., You gonna catch Bat Man?

Yellow-Green Sunlight Peak

Social Justice and Colors White: The presence of all colors of the spectrum Black: The absence of all colors of the spectrum So, is the terminology racist? Clean, good, godly, spiritually pure, innocent, untainted, morally beyond reproach. Star Wars, God vs. Satan, The good guy wears white. Found in the light. Dirty, evil, devilish, spiritually impure, guilty, tainted, morally reproachable. Lost in the dark. The Bad guy wears black.

Thin Layer Interference Bubbles

Thin Layer Interference Diesel Rainbow

Thin Layer Interference

Soap Bubble Refraction

Polarization

Polarized Light + 3D Viewing

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