Electromagnetic Waves Ch 18.1

Electromagnetic waves travel as fast as the speed of light True False Statement Electromagnetic waves are longitudinal waves consisting of electric and magnetic fields Electromagnetic waves can travel though all mediums and through a vacuum/empty space Electromagnetic waves travel as fast as the speed of light Electromagnetic radiation can behave like waves and like particles Intensity of light increases as the photons travel farther from the source

Electromagnetic Waves Transverse waves consisting of changing electric and magnetic fields

Electromagnetic Waves Produced by: Travel by: An electric charge vibrating or accelerating Electric field- produced by charged particles & magnetic fields Magnetic field- produced by magnets, by changing electric fields & vibrating charges Vacuum or empty space, as well as matter Magnetic fields and electric fields regenerate each other traveling in the form of a wave Electromagnetic Radiation Transfer of electromagnetic waves through matter

Speed of Electromagnetic Waves Speed of Light Michelson’s Experiment Used mirrors to calculate the speed of light Light is faster than sound Lighting 1st Thunder 2nd 3.00 x 108 m/s When in a vacuum Same for electromagnetic waves

Wavelength & Frequency In a vacuum all electromagnetic waves travel at the same speed Outside Different wavelengths and frequencies SI Units V= f = Hz λ= m

Math Practice 1. 3. 2.

Wave or Particle? Electromagnetic radiation behaves sometimes like waves and like a stream of particles

Waves and Particles Wave Model Particle Model Bright Bands indicate constructive interference Dark Bands indicate destructive interference Photon- packets of electromagnetic energy Blue light – high frequency photon Emission of electrons Red light- lower frequency photon No emission of electrons

Intensity Rate at which a waves energy flows through a given area Decreases as photons travel farther from the source

Electromagnetic Spectrum Ch 18.2

Infrared rays can be felt by your skin, and can be very harmful True False Statement Radio waves include microwaves, tv, and radar waves- which have the longest wavelengths=low frequency Infrared rays can be felt by your skin, and can be very harmful Ultraviolet rays help your body produce vitamin D, which helps absorb Ca Xrays are absorbed by bones and too much can kill living tissue Gamma rays are used to kill cancer cells

Waves of the Spectrum Electromagnetic Spectrum Includes: Full range of frequencies of electromagnetic radiation Includes:

Radio Waves Longest wavelengths in the spectrum Lowest frequencies 300,000 MHz or less

Radio Waves Television Radio Weather and location can affect reception of signal Amplitude modulation (AM) Amplitude is varied, frequency stays the same Frequency modulation (FM) Frequency is varied, amplitude stays the same

Radio Waves Microwaves Radar Radio Detection and Ranging Doppler Effect Radio waves are sent out, reflected, bounce back and picked up by a receiver Shortest radio wave Penetrate food only to a few centimeters Also carry cell phone conversations

Infrared Rays Higher frequencies than radio Lower than red light Used as a source of heat or to detect heat differences Can’t see it but can feel its warmth Thermograms

Visible Light Ultraviolet Light Light that the human eye can see Higher frequencies than violet light In moderation Help skin produce vitamin D, which helps absorb Ca In excess Causes sunburn, skin cancer, wrinkles Kill microorganisims

X Rays Gamma Rays Very short wavelength, higher frequencies than ultraviolet Bone and teeth Absorb Xrays , show densities Too much exposure Kills living tissue Shortest wavelengths, highest frequencies Used to kill cancer cells, and take pictures of the brain Overexposure deadly

Behaviors of Light Ch 18.3

Materials can be transparent, translucent or opaque True False Statement Materials can be transparent, translucent or opaque Diffuse reflection is due to reflection off of a rough surface A mirage is a false or distorted image due to reflection Polarization waves vibrate in all direction unlike normal light that vibrates in one plane Scattering of light is why the sky looks blue, clouds look white, and the sun setting looks red

Light and Materials Without light, nothing is visible Transparent Material Transmits light (light passes through) Translucent Material Scatters light Can see through object, but looks cloudy Opaque Material Absorb or reflect light No light passes through

Interactions of Light When light strikes a new medium the light can be Reflected Absorbed Transmitted Refracted Polarized Scattered

Interactions of Light Reflection Refraction Regular Reflection Parallel light strikes a surface and reflect all in the same direction Diffuse Reflection Parallel light strikes a rough, uneven surface and reflect in many different direction Cause mirages False distorted images Occur because Light travels faster in hot air than cold

Interactions of Light Polarization Scattering Light with waves that vibrate in only one plane Light is redirected as it passes through a medium Sunrise/Sunset Tiny particles scatter blue light- you see the red light Blue Sky Blue light is scattered in all directions- blue sky even though colorless

Color Ch 18.4

White light separates into the color spectrum(ROYGBIV) True False Statement White light separates into the color spectrum(ROYGBIV) Color of an object depends only on what color of light shines on the object Primary Colors of light at red, blue and green, while primary pigments are cyan, yellow and magenta A primary color + a secondary color = white light A pigment + a pigment = black pigment

White Light = Colors White light passes through a prism Shorter wavelengths refract more than longer wavelengths The colors separate Process of white light separating into colors Dispersion

Colors of Objects Color depends on What the object is made of The color of light that strikes the object

Mixing Colors of Light Primary Secondary Red, Green, Blue If both light colors hit a surface, they mix to form a new color Secondary Cyan, Yellow, Magenta Primary+Secondary= White Complimentary color of light

Mixing Pigments Pigment Primary Pigments 2 Pigments= Black Reflects some colors Absorbs some colors Paints, inks, dyes, photos… Primary Pigments Secondary Colors Cyan, Yellow, Magenta 2 Pigments= Black Complementary Colors of Pigments

Sources of Light Ch 18.5

A luminous object glows when light is shined on it True False Statement A luminous object glows when light is shined on it An incandescent light (light bulb) has a filament, while a fluorescent light (energy efficient) has photons A laser also has photons, but emits radiation Neon lights color depends on the color of the tube Sodium vapor and tungsten halogen lights are the same

Light Luminous Objects that give off their own light Sun, flashlights, fireflies…

Types of Light Fluorescent Incandescent Absorbs light at one wavelength, emits light at longer wavelength Phosphor- solid that emits light by steadily emitting photons Object gets hot enough to glow Electrons flow through the filament of the bulb The filament gets hot and emits light

Types of Light Neon Laser Light Amplification by Stimulated Emission of Radiation Generates a beam of coherent light Solid, liquid or gas emits photons Emit light when electrons move through a gas or mixture of gases inside glass tubing

Types of Light Sodium Vapor Tungsten Halogen Solid sodium, with neon and argon gas Electric current passes bulb, it ionizes, heats up and causes sodium to turn into a gas Electrons flow through a tungsten filament, which gets hot and emits light