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

Electromagnetic Waves                     

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

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Nature of Electromagnetic Waves They are Transverse waves without a medium. (They can travel through empty space) They are Transverse waves without a medium. (They can travel through empty space) They travel as vibrations in electrical and magnetic fields. They travel as vibrations in electrical and magnetic fields. Speed of electromagnetic waves = speed of light: 300,000,000 meters/second 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.) (Takes light 8 minutes to move from the sun to earth {150 million miles} at this speed.)

When an electric field changes, so does the magnetic field. When one field vibrates—so does the other. When an electric field changes, so does the magnetic field. When one field vibrates—so does the other. RESULT- RESULT- An electromagnetic An electromagneticwave. Click here  Animation: Interaction of vibrating charges Click here  Animation: Interaction of vibrating chargesInteraction of vibrating chargesInteraction of vibrating charges

Waves or Particles Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles. Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles. Example: Light Example: Light Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses. 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 A “particle” of light is called a photon

Waves of the Electromagnetic Spectrum Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency Click here  (Animation—Size of EMwaves) Click here  (Animation—Size of EMwaves)—Size RADIO WAVES MICROWAVES INFRARED RAYS VISIBLE LIGHT ULTRAVIOLET RAYS X-RAYS GAMMA RAYS

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

MRI of the Brain

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

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

MICROWAVES Microwaves—have the shortest wavelengths and the highest frequency of the radio waves. Microwaves—have the shortest wavelengths and the highest frequency of the radio waves. Used in microwave ovens. 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. 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. Used by cell phones and pagers. RADAR (Radio Detection and Ranging) 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.) (Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.)

Warm Up 1. Draw the EM spectrum. 1. Draw the EM spectrum. 2. What is a medium? 2. What is a medium? 3. Do EM waves need a medium to travel? 3. Do EM waves need a medium to travel? 4. What is a “vacuum”? 4. What is a “vacuum”? 5. What is a niche? Give an example. 5. What is a niche? Give an example. 6. What is ecology? 6. What is ecology?

INFRARED RAYS Infrared= below red Infrared= below red Shorter wavelength and higher frequency than microwaves. Shorter wavelength and higher frequency than microwaves. You can feel the longest ones as warmth on your skin You can feel the longest ones as warmth on your skin Heat lamps give off infrared waves. Heat lamps give off infrared waves. Warm objects give off more heat energy than cool objects. 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. 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.

Night vision goggles Remote controls

VISIBLE LIGHT Shorter wavelength and higher frequency than infrared rays. Shorter wavelength and higher frequency than infrared rays. Electromagnetic waves we can see. Electromagnetic waves we can see. Longest wavelength= red light Longest wavelength= red light Shortest wavelength= violet (purple) 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. 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 Shorter wavelength and higher frequency than visible light Shorter wavelength and higher frequency than visible light Carry more energy than visible light Carry more energy than visible light Used to kill bacteria. (Sterilization of equipment) Used to kill bacteria. (Sterilization of equipment) Causes your skin to produce vitamin D (good for teeth and bones) Causes your skin to produce vitamin D (good for teeth and bones) Causes Sun burn Causes Sun burn Some animals can see in UV (bees) Some animals can see in UV (bees)

Ultraviolet (cont.) UVA UVB and UVC Energy Highest of UV waves Lower than UVA Health risks Extremely low risk for DNA damage Extremely low risk for DNA damage Can destroy Vitamin A in skin Can destroy Vitamin A in skin Can cause DNA damage, leading to skin cancer Can cause DNA damage, leading to skin cancer Responsible for sunburn Responsible for sunburn

X- RAYS *Shorter wavelength and higher frequency *Shorter wavelength and higher frequency than UV-rays than UV-rays *Carry a great amount of energy *Carry a great amount of energy *Can penetrate most matter. *Can penetrate most matter. Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed) Bones and teeth absorb 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 Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure) (lead vest at dentist protects organs from unnecessary exposure) Used by engineers to check for tiny cracks in structures. Used by engineers to check for tiny cracks in structures. The rays pass through the cracks and the cracks appear dark on film. The rays pass through the cracks and the cracks appear dark on film.

GAMMA RAYS Shorter wavelength and higher frequency than X-rays Shorter wavelength and higher frequency than X-rays Carry the greatest amount of energy and penetrate the most. Carry the greatest amount of energy and penetrate the most. Used in radiation treatment to kill cancer cells. Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly. Can be very harmful if not used correctly.

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. 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. 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 AnimationAnimation—View a Galaxy at different wavelengths AnimationSong: rrCI&safe=active

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