6 - 6.1 The Wave Nature of Light • Visible light-form of radiation or radiant energy o Electromagnetic radiation • Electromagnetic spectrum

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Unformatted text preview: 6.1 The Wave Nature of Light • Visible light-form of radiation or radiant energy o Electromagnetic radiation • Electromagnetic spectrum 200-700 nm Figure 6.4 (homework) pg. 219 • Electromagnetic radiation is characterized by wave nature • All wave have a wavelength ( λ )-distance between successive peaks • The wavelength, Units: nanometers (nm)=1 x 10-9 m • The amplitude, A, the intensity of the wave • The frequency, ν (nu)-# of cycles per second Units: cycles/second (sec-1), Hertz, Hz Figure 6.2 (a) • Infrared has a lower frequency and a higher wavelength than visible light • The speed of a wave, v, is given by the (frequency)(wavelenght) • For light, speed=c= νλ (speed=speed of light constant x wavelength) • Speed of light constant, c=3.00 x 108 m/sec o Ex: • The yellow light given off by the sodium vapor lamp used for public lighting has a wavelength of 589 nm. What is the frequency of the radiation? λ =589 nm c= νλ ν =c/ λ =(3.00 x 108 m/sec)/589 x 10-9 m =5.09 x1014 s-1 6.2 Quantized Energy Photons • Planck-energy can only be absorbed or released from atoms in certain amounts called quanta • A quanta- smallest amount of energy • The relationship b/t energy and frequency is o E=h ν (energy=Plank's constant x frequency) • h=Plank's constant=6.63 x 10-34 -s • Plank states that energy is absorbed in whole number multiples of h ν so, 1 h ν , 2 h ν , 3 h ν …. • Therefore, E=nh ν • The Photoelectric Effect and Photons o Photoelectric Effect-emission of electrons from a metal surface exposed to radian energy • Figure 6.7 o Quantized-energy produced in a specific amount • If light shines on the surface of a metal, electrons are emitted in specific amounts or quantized then the energy released or absorbed is also quantized o The electrons will only be ejected once the threshold frequency is reached • Below the threshold frequency, no electrons are released • Above the threshold frequency, the # of electrons is dependent on the intensity of the light o Einstein assumed that light traveled in energy packets called photons • The energy of one photon: E=h ν (Plank's constant x frequency) • Einstein concluded that photons are also quantized • Since atoms can only absorb or emit energy that is quantized, then the energy levels of an atom are also quantized Example: Calculate the energy of one photon of yellow light whose wavelength is 589 nm....
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This note was uploaded on 04/25/2008 for the course V 011 taught by Professor Staff during the Fall '06 term at NYU.

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6 - 6.1 The Wave Nature of Light • Visible light-form of radiation or radiant energy o Electromagnetic radiation • Electromagnetic spectrum

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