Transcript Slide 1
The electromagnetic spectrum Includes more that just Visible light. Visible light is electromagnetic radiation with wavelengths from 400 to 700 nm. An electromagnetic wave is A transverse wave consisting Of oscillating electric and Magnetic fields at right Angles to each other. Electromagnetic waves vary Depending on frequency and wavelength, this is Called the spectrum. Classification Applications Radio Waves AM or FM radio and television Microwaves Radar, Microwaves ovens Heat, photography, physical therapy Infrared Waves Visible Light Seeing, photography Ultraviolet Light Sterilization X-Rays Medical Exams Gamma Rays Cancer Treatment All electromagnetic waves Move at the speed of light. c=fλ C = 2.998 X 108 The AM radio band extends From 5.4 X 105 Hz to 1.7 X 106 Hz. What are the Longest and shortest wavelengths In this frequency range? 560 m and 180 m A luminous body is one that Emits light waves. An illuminated body simply Reflects light waves produced From an outside source. Waves can be approximated As rays for easier drawing And visualization. Brightness decreases by the Square of the distance from The source. This is called the inverse Square law. The Candela is the SI base unit Of luminous intensity, It is also called a candle power. Luminous flux (P) is the rate at Which light is emitted from a Source. A lumen is a unit of Luminous flux. Illuminance (E) is the rate at which Light falls on a surface. Lux is a unit of illuminance, Lumens per square meter. P E= 4πd2 What is the illumination on Your desktop if it is lighted by A 1750 lm lamp that is 2.5m Above your desk? E = 22.3 lx In 1665, Francesco Grimaldi Observed that the edges of a Shadow are not perfectly sharp. He also noted that the shadow Was bordered by colored bands. Grimaldi recognized this Phenomenon as diffraction, Which is the bending of light Around a barrier. Additive primary colors produce White light when combined. Subtractive primary colors Filter out all light when combined. A primary color is a color from Which all other colors Can be derived. A secondary color formed by A pair of two primary colors. A complementary color is two Colors of light which when added Together produce white light. A dye is a molecule that absorbs Some light wavelengths and Reflects or transmits others. A pigment is a colored material That absorbs certain colors And reflects or transmits Other colors. A primary pigment is a pigment That absorbs only one color from white light. A secondary pigment is a pigment that absorbs two primary Colors from white light. Thin-film interference is light Interference caused by reflection From the front and back surface Of a thin layer of liquid. Color All visible colored light together produce white light (ex. sunlight). • White is not a single color, but a combination of all colors. • White objects reflect all colors. Black is not a single color – it is the absence of light. • Black objects absorb all frequencies of light. • They reflect only enough light so that you can see them. • An object’s color depends on which light frequencies are reflected and which are absorbed. – Ex: A blue shirt appears blue because it absorbs all colors EXCEPT blue. It reflects the blue back to our eyes. – Ex: A plant leaf is green because it absorbs all the colors BUT green to use for photosynthesis. Linear polarization is the Alignment of electromagnetic Waves in such a way that the Vibrations of the electric fields In each of the waves are Parallel to each other.