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Bohr’s Third Postulate. A single photon is emitted whenever an electron jumps down from one orbit to another. Why do astronomers often use the terms color and temperature interchangeably when referring to stars?
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Bohr’s Third Postulate A single photon is emitted whenever an electron jumps down from one orbit to another.
Why do astronomers often use the terms color and temperature interchangeably when referring to stars? • Why did Bohr assume that the electrons do not radiate when they are in the allowed orbits?
In quantum mechanics the amplitude of a particle wave is called the wave function and is given the symbol Y.
If we are dealing only with one photon: At any point the square of the electric field strength is a measure of the probability that a photon will be at that location.
For a single particle: Y2 at a certain point in space and time represents the probability of finding the electron at the given position and time.
Important: there is no way to predict where one electron would hit the screen. We could predict only probabilities.
The main point of this discussion is this: if we treat electrons as if they were waves, then Y represents the wave amplitude. If we treat them as particles, then we must treat them on probabilistic basis.
The act of observing produces a significant uncertainty in either the position or the momentum of electron.
Position uncertainty of a baseball What is the uncertainty in position, imposed by the uncertainty principle, of a 150-g baseball thrown at 42+-1 m/s? Should the umpire be concerned? Can he use Heisenberg as an excuse?
Baby-Quiz • If all objects emit radiation, why don’t we see most of them in the dark? • Suppose you were a nineteenth-century scientist who had just discovered a new phenomenon known as Zeta rays. What experiment could you perform to define if Zeta rays are charged particles or e/m waves? Could this experiment distinguish between neutral particles and an e/m wave? • If a metal surface is illuminated by light at a single frequency, why don’t all the photoelectrons have the same kinetic energy when they leave the metal’s surface? • What property of the emitted electrons depends on the intensity of incident light?What property of the emitted photoelectrons depends on the frequency of incident light?
