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Physics and the Quantum Mechanical Model Section 13.3

Physics and the Quantum Mechanical Model Section 13.3. KEY TERMS: Amplitude Wavelength Frequency Electromagnetic Spectrum Emission Spectrum Photoelectric Effect Ground State. Key Concepts. The product of frequency ( ν ) and wavelength ( λ ) always equals the speed of light (c)

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Physics and the Quantum Mechanical Model Section 13.3

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  1. Physics and the Quantum Mechanical ModelSection 13.3 • KEY TERMS: • Amplitude • Wavelength • Frequency • Electromagnetic Spectrum • Emission Spectrum • Photoelectric Effect • Ground State

  2. Key Concepts • The product of frequency (ν) and wavelength (λ) always equals the speed of light (c) c = λν • Line emission spectra illustrate the amount of quantized energy levels • De Broglie proposed that all matter in motion has wavelength properties • Photoelectric Effect – metals eject electrons called photoelectrons when light shines on them • Only certain frequencies of light will demonstrate the photoelectric effect

  3. Light and Atomic Spectra

  4. Electromagnetic Spectrum and how wavelength relates to various objects

  5. Frequency = number of complete waves per unit of time Units = Hertz (Hz) or per second (sec-1) Amplitude = wave’s height from the origin Wavelength = The length of one complete wave cycle Units = Ǻ, nm, cm, m • Wavelength (λ) and Frequency (ν) are inversely related • Speed of light = wavelength x frequency • c = λν • As wavelength increases, frequency decreases

  6. Electromagnetic Spectrum – various colors you see due to the wavelength of light Emission Spectrum – line of color that correlates to one exact frequency

  7. Photoelectric effect • Max Planck studied this concept • Trying to describe why iron (or metals in general) changed color when heated • Energy of a quantum = Planck’s constant x frequency • E = h ν • The size of the quantum being absorbed or emitted depends on the size of the energy change • Small energy change = low frequency radiation • Large energy change = high frequency radiation

  8. Photoelectric Effect • Albert Einstein • Proposed that light can be described as quanta of energy that behave as if they were particles • Photons = light energy • Metals eject electrons when specific wavelengths of light shines on them Electrons being ejected Light energy metal

  9. Application of photoelectric effect: Photoelectric cells uses the energy of light to generate electricity for homes, vehicles, etc

  10. Atomic Spectra • Electrons absorb energy and get “excited” • When they are excited, they jump up to a new energy level (farther away from nucleus) • The electron then loses that energy and falls back down to ground state • The energy emitted produces the various colors of light that you see

  11. Quantum Mechanics • If light behaves as waves and particles, can particles behave as waves? • Question proposed by De Broglie (French graduate student) • All matter exhibits wavelike motions • Particles gain or lose energy in packages called quanta • Heisenberg uncertainty principle • It is impossible to know exactly both the velocity and position of a particle at the same time

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