Electromagnetic waves the electromagnetic spectrum
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Electromagnetic Waves & the Electromagnetic Spectrum. Electricity can be static, like what holds a balloon to the wall or makes your hair stand on end. . Magnetism can also be static like a refrigerator magnet. But when they change or move together, they make waves - electromagnetic waves.

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Electromagnetic Waves & the Electromagnetic Spectrum

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Electromagnetic waves the electromagnetic spectrum

Electromagnetic Waves &the Electromagnetic Spectrum


Electromagnetic waves the electromagnetic spectrum

  • Electricity can be static, like what holds a balloon to the wall or makes your hair stand on end.


Electromagnetic waves the electromagnetic spectrum

  • Magnetism can also be static like a refrigerator magnet.

  • But when they change or move together, they make waves - electromagnetic waves.


Electromagnetic waves

Electromagnetic waves

  • Formed when an electric field (blue arrows) couples with a magnetic field (red arrows).

  • The magnetic and electric fields of an em wave are perpendicular to each other and to the direction of the wave.


Electromagnetic waves1

Electromagnetic Waves

  • Transverse waves without a medium!

  • (They can travel through empty space)


Electromagnetic waves the electromagnetic spectrum

  • They travel as vibrations in electrical and magnetic fields.

    • Have some magnetic and some electrical properties to them.


Electromagnetic waves the electromagnetic spectrum

  • When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibratesso does the other.

  • RESULT-An electromagnetic wave.


Electromagnetic waves the electromagnetic spectrum

  • Electromagnetic waves travel VERY FAST around 300,000 kilometres per second (the speed of light).

At this speed they can go around the world 8 times in one second.


Electromagnetic waves the electromagnetic spectrum

  • 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.

      • Light as particles (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)


Electromagnetic waves the electromagnetic spectrum

  • Electromagnetic Spectrumname for the range of electromagnetic waves when placed in order of increasing frequency

GAMMA RAYS

ULTRAVIOLET RAYS

RADIO WAVES

INFRARED RAYS

X-RAYS

MICROWAVES

VISIBLE LIGHT


Electromagnetic waves the electromagnetic spectrum

Notice the wavelength is

long (Radio waves) and gets shorter (Gamma Rays)


Ionizing radiation vs non ionizing radiation

Ionizing Radiation vsNon-ionizing Radiation

  • Ionizing

    • radiation that is strong enough to damage molecules and cells

    • includes the higher frequency forms of UV radiation, all X-radiation and all gamma radiation

  • Non-ionizing

    • includes the lower frequency forms of UV radiation, and all forms of radiation below(visible, IR, microwave, and radio wave radiation).


Electromagnetic waves the electromagnetic spectrum

Background radiation: Low levels of radiation from both natural and man-made sources that is always around us.

  • Natural background radiation examples

    • gamma radiation that penetrates our atmosphere from outer space

    • radiation released from rocks, soil, and water.

  • Man-made sources of radiation

    • fallout from nuclear weapons testing

    • radiation released into the environment from coal-burning and nuclear power plants.


Radio waves

RADIO WAVES

  • Have the longest wavelengths and lowestfrequencies of all the electromagnetic waves.


Electromagnetic waves the electromagnetic spectrum

  • Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite.


Electromagnetic waves the electromagnetic spectrum

  • A radio picks up radio waves through an antenna and converts it to sound waves.

    • Each radio station in an area broadcasts at a different frequency.

      • # on radio dial tells frequency.


Electromagnetic waves the electromagnetic spectrum

  • MRI

  • (MAGNETIC RESONACE IMAGING)

    • Uses Short wave radio waves with a magnet to create an image.


Microwaves

MICROWAVES

  • Have the shortest wavelengths and the highest frequency of the radio waves.


Electromagnetic waves the electromagnetic spectrum

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.


Radar

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.


Electromagnetic waves the electromagnetic spectrum

A remote control uses light waves just beyond the visible spectrum of lightinfrared light wavesto change channels on your TV.


Electromagnetic waves the electromagnetic spectrum

  • You can feel the longest ones as warmth on your skinWarm objects give off more heat energy than cool objects.


Electromagnetic waves the electromagnetic spectrum

Therefore people give off infrared rays.

Heat lamps give off infrared waves.

Thermograma picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off.


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


Ultraviolet rays

ULTRAVIOLET RAYS

  • Shorter wavelength and higher frequency than visible light

  • Carry more energy than visible light


Uv waves are invisible to the human e ye

UV Waves are Invisible to the Human Eye

  • Bees, along with some birds, reptiles and other insects, can see near-ultraviolet light reflecting off of plants.

  • Bug zappers attract insects with ultraviolet light to lure them to the trap.


Ultraviolet astronomy

ULTRAVIOLET ASTRONOMY


Aurorae

AURORAE


X rays

X- RAYS

  • Shorter wavelength and higher frequency than UV-rays

  • Carry a great amount of energy

  • Can penetrate most matter.


Electromagnetic waves the electromagnetic spectrum

Bones and teethabsorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)


Electromagnetic waves the electromagnetic spectrum

  • Too much exposure can cause cancer

    • (lead vest at dentist protects organs from unnecessary exposure)


Electromagnetic waves the electromagnetic spectrum

  • 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.


Sources of gamma rays

SOURCES OF GAMMA RAYS

  • Produced by the hottest and most energetic objects in the universe

    • neutron stars and pulsars

    • supernova explosions

    • regions around black holes

  • On Earth - generated by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.


Exploding nuclear weapons emit gamma rays

Exploding nuclear weapons emit gamma rays.


Gamma rays in medicine

Gamma Rays in Medicine

  • They are able to penetrate most materials and aren't easily blocked.

  • When they pass through matter, they eject electrons from the atoms they collide with.

    • This is called ionization, and it's dangerous to living cells; prolonged gamma radiation can lead to grave illness and even death.

  • Yet we use gamma rays from cobalt-60 for cancer treatment.

  • We also use gamma rays in industry to test castings and welded joints for tiny, almost invisible cracks or defects.


Electromagnetic waves the electromagnetic spectrum

  • Used in radiation treatment to kill cancer cells.

  • Can be very harmful if not used correctly.


Electromagnetic waves the electromagnetic spectrum

  • The Incredible Hulk was the victim of gamma radiation.


Gamma knife surgery

Gamma Knife surgery

  • > 200 beams of gamma radiation are directed at small tumors

    • causing 90 to 95 % of them to cease growing and a majority of them to shrink

    • malignant and benign tumors and Parkinson's disease.

  • PET (Positron Emission Tomography) scan

    • patient is injected with a radioactive substance and placed on a table that slides into a gamma ray detector.

    • Doctors can then track blood flow and other biochemical processes within the body


I nternational s ecurity and food s afety

International Security and Food Safety

  • Container Security Initiative

  • By 2008, 58 ports worldwide were equipped with X-ray and gamma ray screening devices, giving security officers access to 86 percent of all maritime cargo in containers

  • Irradiation pasteurization" or cold pasteurization

    • passing food through a beam of gamma rays

    • kills bacteria that could spoil food or render it poisonous

    • food that is irradiated today does not become radioactive itself, and is considered safe.


Why are gamma rays more harmful than radio waves

Why are Gamma Rays More Harmful than Radio Waves?


In conclusion

In Conclusion

  • All forms of electromagnetic radiation have important applications and uses

  • Exposure to non-ionizing radiation (lower frequency) forms of EMR is relatively harmless

  • Exposure to ordinary forms and amounts of radiation is not harmful (you have been exposed to all forms of EMR every day of your life)

  • Among those forms to which we should limit our exposure, there are important and helpful uses

  • We can harvest the energy in the electromagnetic radiation from the sun to produce power


Electromagnetic waves the electromagnetic spectrum

  • Continued SUMMARY

  • All electromagnetic waves travel at the same speed. (300,000,000 meters/second) in a vacuum.

  • They all have different wavelengths and different frequencies.

    • Long wavelength-lowest frequency

    • Short wavelength highest frequency

    • The higher the frequency the higher the energy.


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