Electromagnetic Waves

1. Electromagnetic Waves Ch 18.1

3. Electromagnetic Waves • Transverse waves consisting of changing electric and magnetic fields

4. 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

5. Speed of Electromagnetic Waves Michelson’s Experiment Speed of Light • 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

6. 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

7. Math Practice • 1. • 3. • 2.

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

9. 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

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

11. Electromagnetic Spectrum Ch 18.2

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

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

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

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

17. 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

18. 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

19. 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

21. Behaviors of Light Ch 18.3

23. 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

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

25. 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

26. 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

28. Color Ch 18.4

30. 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

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

32. Mixing Colors of Light • Primary • 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

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

35. Sources of Light Ch 18.5

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

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

39. Types of Light Laser Neon • 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

40. 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