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Electromagnetic Spectrum and Quantized Energy

Electromagnetic Spectrum and Quantized Energy. Why the electron is what it is. What is a wave?. A wave is a transfer of energy from one point to another via a traveling disturbance A wave is characterized by its wavelength, frequency, and amplitude. Transverse .

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Electromagnetic Spectrum and Quantized Energy

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  1. Electromagnetic Spectrum and Quantized Energy Why the electron is what it is

  2. What is a wave? • A wave is a transfer of energy from one point to another via a traveling disturbance • A wave is characterized by its wavelength, frequency, and amplitude

  3. Transverse • Waves that travel perpendicular to the direction of motion • Examples: Light, -p wavesfor earthquakes, Ocean waves 

  4. Wavelength (λ) • Distance from successive crest to crest or trough to trough • Measured in meters

  5. Frequency • Number of crests passing by per second • Measured in Hertz (Hz) defined to be one cycle per sec • Equal to the inverse of the amount of time it takes one wavelength to pass by

  6. Wave Speed Traveling Waves move through space at a certain speed Where, v is the speed of the wave (m/s) λis the wavelength in meters (m) f is the frequency in Hertz (cycle/s)

  7. Matter / Quantum Waves • Electrons and other tiny particlesshow wave-like properties • A particle moving close to the speed of light (c) can diffract or bend around the edges of objects • Also, particles do exhibit interference which is a wavelike property    • Any moving matter has wave characteristics in theory BUT the wavelength of any life-size particle, like a golf ball, is so small that it is negligible • To learn about matter waves in depth go on to the next slide.

  8. If we can sometimes consider an electron to be a wave, what is its wavelength?

  9. Its wavelength depends on its momentum or where p is momentum in kg*m/s, h is Planck’s constant = 6.63 x 10-34 J, and λ is the wavelength in meters

  10. What is Planck’s constant? • Planck’s Constant is the size where quantum mechanics becomes necessary • Since "Planck's Constant" (‘h’= 6.63 x 10 - 34 Js) is such a tiny number, quantum mechanics is needed only at very small scales • An electron also has spin that is quantized in units of h. • These units (Joule-sec) are units of angular momentum

  11. Electromagnetic Waves • Waves of energy emitted from any accelerating charges • Any object that is above absolute zero emits electromagnetic waves • The entire range of possibilities is called the “Electromagnetic Spectrum” • Still confused? Then click What are electromagnetic waves? • To learn about the wavelength of photons click to the next slide.

  12. Electromagnetic Waves • Wavelength is : Where, c is the speed of light (3 x 108 m/s in a vacuum) λ is the wavelength in meters f is the frequency in Hertz And h is Planck’s constant (there it is again- do you remember its value?) E is the energy of a photon in Joules

  13. What is this “photon” term you’re throwing in there? • A photon is a bundle (quantum) of light • A photon has energy equal to Recall that h is Plank’s constant ν is the frequency of the radiation (wave)

  14. What does a photon do? • Both magnetic and electric forces involve the exchange of photons • The photon has zero rest mass, but has momentum, can be deflected gravity, and can exert a force

  15. X-RAYS • Emitted when an electron moves from certain excited states back down to its ground state, or when an electron that is moving very quickly is suddenly stopped • Two groups - long wavelength (soft x-rays) and shorter wavelength (hard x-rays) • Used for radiography (x-ray photography) and to look at materials in industry for defects • Sources:  emitted by heavy atoms after bombardment by an electron

  16. ULTRAVIOLET • Above the color violet  • Three groups - UV A, UV B, and UV C. • “A” type: longest wavelength; least harmful • UV B and UV C are absorbed by DNA in cells  • Used by the body to produce vitamin D, to kill bacteria on objects, and for sun tanning • Sources:   Ultra hot objects 5000°C or more

  17. VISIBLE LIGHT • White light: combination of all the colors • Rainbow: example of white light that has been separated into a continuous spectrum of colors • The names of colors are assigned in order of their wavelengths • Used for communications (fiber optics) • Sources:   very hot objects

  18. INFRARED • Thought of as heat but is not always • Far infrared energy is heat energy. • All objects that have warmth radiate infrared waves • Easily absorbed and re-radiated.  • Used in remote controls,  surveillance, therapy of muscles • Sources:  Humans, the sun

  19. MICROWAVES • 1 mm-1 dm in length • Absorbed by water molecules – how microwave ovens heat food • Used in telecommunications and power transmission • Sources:  electric circuits, many stars, microwave ovens

  20. RADIO WAVES • 10 cm- 100,000+m  in length • Only cosmic waves the reach the surface of the Earth • Cause of noise • Divided into smaller frequency dependent groups called bands   • Used for communications • Sources:  transmitters and sparks from motors

  21. So What is this Quantum Thing? • A Quantum is the Energy required to jump an Electron from one orbit to another.

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