Physics 1 H Created by Stephanie Ingle Light and Color Physics 1 H Created by Stephanie Ingle

Light Light is a transverse wave. Light waves are electromagnetic waves--which means that they do NOT need a medium to travel. Light waves behave like other waves and have the same characteristics such as amplitude, frequency, and wavelength.

Characteristics of Light Intensity (brightness) -- represented by amplitude Color -- determined by frequency Wave speed - depends on the medium Light waves as well as ALL Electromagnetic waves travel with a speed of 3.0 x 108 m/s in a vacuum.

Luminous Flux (P) Luminous flux is the rate at which light energy is emitted from the source. Equivalent to Power Measured in lumens (lm)

Luminous Intensity (I) The amount of light (luminous flux) that falls on one square meter at a distance of 1 meter from the source. Equivalent to Intensity at r = 1 m Measured in candelas (cd) I = P/4 or cd = lm/4

Luminous vs Illuminated a body that emits light has luminous flux Illuminated a body that reflects light no luminous flux does not emit light of its own

Illuminance (E) E = P/(4r2) Amount of light that falls on a surface Intensity of light at any given distance from source measured in lux lux = lumen/m2 r bulb E = P/(4r2)

Other Electromagnetic Waves Radio Microwaves Infrared Ultraviolet X-rays Gamma Rays Radar All of these follow the same rules as Light and travel at the same speed. Light is simply a way of referring to the visible portion of the electromagnetic spectrum.

Characteristics of Electromagnetic Waves Made up of 2 components electric field & magnetic field The electric and magnetic fields are perpendicular to each other. A changing electric field will create a magnetic field and a changing magnetic field will create an electric field; therefore the wave propagates itself through space without need of a medium.

Light and Color There are 3 primary colors of light RED, GREEN, & BLUE When these colors of light are mixed… White Light is produced This process is called color addition

Color Addition (Light) Red + Green = Yellow Red + Blue = Magenta Blue + Green = Cyan Red + Green + Blue = White Yellow, Magenta, and Cyan are called the secondary colors of light because they are produced using 2 of the primary colors.

Pigments Pigments work on the principle of color subtraction. The light we see is reflected light. A pigment of a certain color will reflect only that color of light and absorb all other frequencies. Example: A blue shirt will reflect incident blue light and absorb red and green.

Primary Pigments The primary pigment colors are magenta, cyan, and yellow because they absorb only one frequency of color. Yellow absorbs blue and reflects red and green. Cyan absorbs red and reflects blue and green. Magenta absorbs green and reflects red and blue

Color Subtraction (Pigments) Mixing pigments means that you will see only the color that both colors reflect. Red, Blue and Green are secondary pigments because they absorb 2 colors. Magenta + Yellow = Red Cyan + Magenta = Blue Yellow + Cyan = Green

Black and White White light is the mixture of all frequencies (colors) of light. A white surface will reflect all frequencies (colors) of light. Black is not a color! Black is the absence of any light. A black surface will absorb all incident light and reflect none.