chem lecture 4

chem lecture 4 - From the assigned reading, which topic did...

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Chemistry 6A From the assigned reading, which topic did you find the most challenging to digest? A. Blackbody radiation B. Photoelectric effect C. Atomic line spectra D. Wavefunctions and orbitals E. None; I didn’t do the reading 1
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Chemistry 6A Key Concepts & Questions Lecture 4 Views at the end of 1800s: Matter consists of particles, which have mass and whose position in space can be identified. Energy in the form of light (electromagnetic radiation) can be described as a wave, which is massless and delocalized. Matter and energy are distinct. What experimental evidence supports the quantization (“particle nature”) of energy (light)? What ideas and experiments are advanced in support of the wave properties of particles? What is the wave (quantum mechanical) model of the atom?
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Chemistry 6A 3 Mechanical, electrical, and magnetic behavior of macroscopic objects calculated by use of classical theory Experimental results that could not be explained by classical mechanics (late 1800s - ): Blackbody radiation and the UV Catastrophe Photoelectric Effect The Impossible (Rutherford) Atom Atomic Line Spectra Inspired revolutionary theories at the beginning of the 20 th Century…
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Chemistry 6A A couple and a stove emitting electromagnetic radiation of varying wavelengths.
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Chemistry 6A 5 Observation : Hot solid objects emit light of different colors, from the dull red of an electric-stove heating element to the bright white of a light bulb filament. Such light can be dispersed by a prism to produce a continuous color spectrum. The light intensity varies with wavelength, peaking at a wavelength fixed by the source temperature . Objects that are effective emitters are also effective absorbers.
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Chemistry 6A 6 As temperature increases, the maximum intensity shifts to shorter wavelength, producing the familiar color change of solid objects as they are heated to incandescence .
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Chemistry 6A 7 An IDEALIZED OBJECT that absorbs all radiation incident on it (and thus does not reflect any light or heat). The radiation it emits originates from its temperature and is independent of the material of which the blackbody is made. A hallow cube with a small hole in it approximates a blackbody.
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Chemistry 6A 8 Prediction of classical theory : There is no limitation on the amount of energy a system may absorb or emit, and thus, the radiation profile has no maximum and goes to infinite intensity at very short wavelengths. As λ approaches zero, intensity approaches
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Chemistry 6A 9 According to classical mechanics: All matter is made of electrically charged particles that jiggle (“oscillators”) and which emit (and absorb) electromagnetic radiation. The energy of matter is continuous and there are no restrictions on the value of the total energy. It may assume any arbitrary value. A new idea is advanced:
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chem lecture 4 - From the assigned reading, which topic did...

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