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Waves

Waves. EM spectrum. As wavelength increases frequency decreases. Can we interconvert between the two? Units: wavelength= distance (meters, nanometers ect ….) Units frequency= Hz (aka 1/sec) What does c (speed of light) have for units?. Planck’s Quantum Theory.

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Waves

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  1. Waves

  2. EM spectrum As wavelength increases frequency decreases. Can we interconvert between the two? Units: wavelength= distance (meters, nanometers ect….) Units frequency= Hz (aka 1/sec) What does c (speed of light) have for units?
  3. Planck’s Quantum Theory When solids are heated they emit radiation. Planck discovered molecules can only emit light at specialized energies or “quanta” A “quantum” is the smallest quantity of energy and is equal to: h=6.626x10-34J*s
  4. Intensity vs. frequency/wavelength/energy Different semiconductors emit different wavelengths. This is how we make L.E.D.s Different wavelengths/frequencies/energy of light waves show up as different __________ to our eyes. A) brightness B) colors C) sounds D) glowy levels E) I don’t know What makes things__________________?
  5. Problem 1- Conceptual questions A) Red light falls around 700 nm green light falls around 500 nm. Which color is highest in frequency? Which color is highest in energy ? A=Red B=Green C= I don’t know B) Given the electromagnetic spectrum, which is more damaging to the skin, UV or microwaves? Why ? A= UV are more damaging B= Microwaves are more damaging C= I don’t know
  6. Problem 1- Conceptual questions C) UV light is subdivided into classifications UVAI (longest wave), UVAII, UVB and UVC light (shortest). Most UVC light does not reach the surface of earth. Why?  Originally it was thought that only UVA rays caused sun cancer. Given the information about UVC rays not reaching the surface, why might this have been previous common wisdom ? Why isn’t it true? Black lights emit long wave UVA rays along with a very small amount of visible light (seen as purple to our eyes). Does this mean we can develop skin and eye from black lights ? Why?
  7. Problem 2-Freqency to wavelength and wavelength to frequency A) I’ll do this one: The wavelength of radiation when you get an xray is 10.0nm. Find the frequency of the xrays. (3s.f.) . B) You try this one: The frequency of red light from a traffic signal is centered at 4.11x1014Hz. What is the wavelength of this radiation.
  8. Problem 3- Frequency/Wavelength to energy A) I’ll do this one: The frequency of radiation when you get an xray is 3.0x1016 Hz. Find the energy of the xrays. (2s.f.) B) You do this one: The wavelength of red light from a traffic signal is centered at 730 nm. What is the energy of this radiation . (2 s. f.)
  9. Problem 4- Introduction to Blackbody Radiation A)As the voltage is increased, what happens to the light bulb ? B) How does Wein’s Law relate to incandescent lightbulbs of different brands ?
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