# I. Electromagnetic Waves

## Presentation on theme: "I. Electromagnetic Waves"— Presentation transcript:

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

? ? Prompt students to guess what the teal box, then the blue box, is hiding. (Wavelength, Amplitude)

When an electric field changes, so does the magnetic field
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

A. Electromagnetic waves
Produced by the movement of electrically charged particles Can travel in a “vacuum” (they do NOT need a medium) Travel at the 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.) (Also known as EM waves)

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

Wave-particle Duality
Light can behave like a wave or like a particle A “particle” of light is called a photon

Radio waves Have the longest wavelengths and lowest frequencies of all the electromagnetic waves. Uses: TV broadcasting AM and FM broadcast radio ( each channel is a different frequency) Cell phone communication Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens

How does a microwave oven work?
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.)

Infrared Radiation Wavelengths in between microwaves and visible light
Uses: Night vision goggles Remote controls Heat-seeking missiles Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Visible light Only type of EM wave able to be detected by the human eye Violet is the highest frequency light Red light is the lowest frequency light Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Ultraviolet Shorter wavelengths than visible light Uses: Black lights
Sterilizing medical equipment Water disinfection Security images on money There is one more UV slide…

Ultraviolet (cont.) UVA UVB and UVC Energy Highest of UV waves
Lower than UVA Health risks Extremely low risk for DNA damage Can destroy Vitamin A in skin Can cause DNA damage, leading to skin cancer Responsible for sunburn Table will fill in from left to right, top to bottom as you advance through. Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

X-rays Tiny wavelength, high energy waves Uses: Medical imaging
Airport security Inspecting industrial welds Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Gamma Rays Smallest wavelengths, highest energy EM waves Uses
Food irradiation Cancer treatment Treating wood flooring Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Using the EM waves to view the Sun
Animation—View a Galaxy at different wavelengths

B. They all have different wavelength and different frequencies.
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.