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Warm Up. 1. What is energy? 2. What is kinetic energy? How do you calculate it? 3. What is potential energy? 4. What is a transverse wave? Draw and label. 5. What is a longitudinal wave? Draw and label. . Electromagnetic Waves.      . Waves… a review.

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warm up
Warm Up
  • 1. What is energy?
  • 2. What is kinetic energy? How do you calculate it?
  • 3. What is potential energy?
  • 4. What is a transverse wave? Draw and label.
  • 5. What is a longitudinal wave? Draw and label.
electromagnetic waves

Electromagnetic Waves



waves a review
Waves… a review
  • Most waves are either longitudinal or transverse.
  • Sound waves are longitudinal.
  • But all electromagnetic waves are transverse…
slide4

?

?

nature of electromagnetic waves
Nature of Electromagnetic Waves
  • They are Transverse waves without a medium. (They can travel through empty space)
  • They travel as vibrations in electrical and magnetic fields.
  • Speed of electromagnetic waves = speed of light: 300,000,000 meters/second

(Takes light 8 minutes to move from the sun to earth {150 million miles} at this speed.)

slide6
When an electric field changes, so does the magnetic field. When one field vibrates—so does the other.
  • RESULT-
  • An electromagnetic

wave.

  • Click here Animation: Interaction of vibrating charges
slide7
Waves or Particles
  • Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles.
  • Example: Light
  • Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses.
  • A “particle” of light is called a photon
waves of the electromagnetic spectrum
Waves of the Electromagnetic Spectrum
  • Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency
  • Click here (Animation—Size of EMwaves)

ULTRAVIOLET RAYS

INFRARED RAYS

GAMMA RAYS

RADIO WAVES

X-RAYS

VISIBLE LIGHT

MICROWAVES

radio waves
RADIO WAVES
  • A. Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.
  • B. A radio picks up radio waves through an antenna and converts it to sound waves.
  • C. Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.
  • D. MRI (MAGNETIC RESONACE IMAGING)
    • Uses Short wave radio waves with a magnet to create an image
slide13

AM=Amplitude modulation—waves bounce off ionosphere can pick up stations from different cities.

+

slide14

FM=Frequency modulation—waves travel in a straight line & through the ionosphere--lose reception when you travel out of range.

+

microwaves
MICROWAVES
  • Microwaves—have the shortest wavelengths and the highest frequency of the radio waves.
    • Used in microwave ovens.
      • (Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.)
    • Used by cell phones and pagers.
    • RADAR (Radio Detection and Ranging)
      • (Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.)
infrared rays
INFRARED RAYS
  • Infrared= below red
  • Shorter wavelength and higher frequency than microwaves.
    • You can feel the longest ones as warmth on your skin
    • Heat lamps give off infrared waves.
  • Warm objects give off more heat energy than cool objects.
  • Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Therefore people give off infrared rays.
slide18

Night vision goggles

  • Remote controls
warm up1
Warm Up
  • 1. Draw the EM spectrum.
  • 2. What is a medium?
  • 3. Do EM waves need a medium to travel?
  • 4. What is a “vacuum”?
  • 5. What is a niche? Give an example.
  • 6. What is ecology?
visible light
VISIBLE LIGHT
  • Shorter wavelength and higher frequency than infrared rays.
  • Electromagnetic waves we can see.
  • Longest wavelength= red light
  • Shortest wavelength= violet (purple) light
  • When light enters a new medium it bends (refracts: we’ll talk about this tomorrow). Each wavelength bends a different amount allowing white light to separate into its various colors ROYGBIV.
ultraviolet rays
ULTRAVIOLET RAYS
  • Shorter wavelength and higher frequency than visible light
  • Carry more energy than visible light
  • Used to kill bacteria. (Sterilization of equipment)
  • Causes your skin to produce vitamin D (good for teeth and bones)
x rays
X- RAYS
  • *Shorter wavelength and higher frequency

than UV-rays

  • *Carry a great amount of energy
  • *Can penetrate most matter.
  • Bones and teethabsorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)
  • Too much exposure can cause cancer
    • (lead vest at dentist protects organs from unnecessary exposure)
  • Used by engineers to check for tiny cracks in structures.
    • The rays pass through the cracks and the cracks appear dark on film.
gamma rays
GAMMA RAYS
  • Shorter wavelength and higher frequency than X-rays
  • Carry the greatest amount of energy and penetrate the most.
  • Used in radiation treatment to kill cancer cells.
  • Can be very harmful if not used correctly.
gamma rays1
Gamma Rays
  • They are produced by the hottest and most energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around black holes.
  • On Earth, gamma waves are generated by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.
using the em waves to view the sun
Using the EM waves to view the Sun

Animation—View a Galaxy at different wavelengths

Song:

http://www.youtube.com/watch?v=P_PVz8HrrCI&safe=active

slide29
Brief SUMMARY
  • A. All electromagnetic waves travel at the same speed. (300,000,000 meters/second in a vacuum.
  • B. They all have different wavelength and different frequencies.
    • Long wavelength-lowest frequency
    • Short wavelength highest frequency
    • The higher the frequency the higher the energy.
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