 Electromagnetic waves are made from moving charges (protons or electrons)  EM waves are transverse waves  The medium that EM waves pass through are electric and magnetic fields  Electric field  Produced by electrically charged particles and by changing magnetic fields.  Magnetic field  Produced by magnets, by changing electric fields, and by vibrating charges

 They carry energy from one place to another  The transfer of energy using EM waves is called electromagnetic radiation  The electric field oscillates in one direction  The magnetic field oscillates perpendicular to the electric field

 Both the electric and magnetic fields oscillate perpendicular to the direction of travel  EM waves are broken up into categories based on their frequency

 Do not need a medium  Can travel through a vacuum, or empty space, as well as through matter  EM waves traveling through matter or across space is called electromagnetic radiation.  Changing electric fields produce changing magnetic fields and vice versa  Fields regenerate each other

 EM waves travel the same speed when in a vacuum  Speed of light in a vacuum is 3.00 x 10 8 m/s  Remember- all EM waves travel at the same speed in a vacuum but they are not all the same!!!!!

 Speed = wavelength x frequency  Remember-waves are going to travel at the same speed  What is changing then?  Wavelength and frequency are inversely proportional  Wavelength increases, frequency decreases  Wavelength decrease, frequency increases

 EM radiation behaves sometimes like a wave and sometimes like a stream of particles  Thomas Young  1801  Light behaves as a wave  Showed constructive and destructive interference by having a light source and darkened screens

 Photoelectric effect  Emission of electrons from a metal caused by light striking the metal  Blue light causes electrons to be emitted  Red light does not cause electrons to be emitted  Photons  Packets of energy in EM radiation

 Photon’s energy is proportional to frequency  Higher frequency = higher photon energy  Blue light = higher frequency  Red light = lower frequency

 Rate at which a wave’s energy flows through a given unit of area  Brightness of a light  Intensity of a light will decrease as photons travel farther from the source

Radio Microwaves InfraredUltravioletGamma Rays X-Rays Frequency & Energy Increases Wavelength Increases Visible Light

RedViolet ROY G. BIV eded rangerange ellowellow reenreen luelue ndigondigo ioletiolet

 Red nm Blue nm  Orange nm Violet nm  Yellow nm  Green nm

 Radio Waves  Radio waves are used to transmit radio and television signals, as well as cell phone conversations  RADAR  RADAR stands for Radio Detection and Ranging  Uses radio waves and the Doppler shift to measure how fast something is moving  Infrared Waves  Infrared waves are heat waves  The human body gives off heat in the form of infrared waves  We sense infrared waves as heat

 Visible Light  The part of the electromagnetic spectrum that we can see is the visible light  Ultraviolet Waves (UV)  UV waves are what cause you to tan  Excessive UV rays can cause you to sunburn, wrinkle, and eventually skin cancer  UV rays can also be used to disinfect air  X-Rays  Can be used to see a person’s skeleton  Can also be used to see inside packages, suitcases, or tractor trailers

 Gamma Rays  Have the shortest wavelength and the most energy  Exposure to tiny amounts is tolerable, but overexposure is deadly  They are used in medicine to kill cancer cells and take pictures of the brain  Used in industry to examine a tool for weaknesses or defects

 Sir Isaac Newton  In 1666, conducted his first experiments with prisms  When he shone light through a prism, he produced an ordered arrangement of colors, from red to violet  He called this sequence of colors a spectrum  Found that white light is composed of colors

 Color by Addition  Primary Colors of Light  Red  Green  Blue  Combining the correct amount of the primary colors of light to produce different colors is called the additive color process  Secondary Colors of Light  Magenta  Cyan  Yellow

Red Blue Green Yellow Magenta Cyan

 Color by Subtraction  Pigment and Dye absorb certain colors and reflect others  Reflected colors are the colors that we see  Making colors by absorbing different colors is called a subtraction process  Primary Pigment – Absorbs one primary color of light  Yellow  Cyan  Magenta  Secondary Pigment – Absorbs two primary colors of light  Red  Blue  Green

Red Blue Green Yellow Magenta Cyan