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Download Unit 4-3 Noteguide Phsyics and Quantem Mechanical
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Transcript
Unit 4-3 Noteguide Physics and Quantam Mechanical Model Quantum Mechanical Model came from the study of light --Newton thought it was because light consisted of particles…. --later it was confirmed light comes in waves --a complete wave cycle starts at zero to reach its lowest value and returns to zero --amplitude of wave = waves height from zero to crest --wavelength (λ) = distance between crests --frequency (ν) = # of wave cycles to pass a given point per unit of time. Measured in cylces per second = hertz (Hr) --can calculate frequency and wavelength: c = λν --wavelength and frequency of light are inversely proportional to each other. (As one increases, the other decreases) Light consists of electromagnetic waves (radiation) --includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays. --all electromagnetic waves travel in a vacuum at a speed of 2.99a x 108 m/s Spectrum = sunlight passes through a prisim and the different frequencies separate into a rainbow of colors Day 2 Atomic Spectra: --When atoms absorb energy, they electrons jump to a higher energy level and as they lose energy and return to the lower energy level they emit the energy in the form of light --EX: Neon Light in a gas tube --each specific frequency of visible light has its own particular color --when we use a prisim, we can see the frequencies of light emitted by an element separate into distinct lines = atomic emission spectrum --each line in the spectrum corresponds to 1 frequency of light --no 2 elements have the same emission spectrum Similar to how two snowflakes are not the same --emission spectrum useful to study the stars’ make-up Bohr’s model also hypothesized that electrons can jump to higher energy levels. (hydrogen atom only) --electron in its lowest energy level = ground state (quantum # (n) = 1) --when the electron gets excited (not that way silly ) the atom jumps to the excited stage with the n = 2, 3, 4 …. --ok smarty pants, when is the light given off? When the electron goes down an energy level --we can calculate how much electronic transition (jumping from/to energy level) E = h x v (h is constant = 6.626 x 10-34 J) Light given off by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron. --this is why each transition makes a line of a specific frequency in the spectrum Quantum Mechanics Einstein says that light is explained as quanta of energy (behave as wave particles) = photons --De Broglie uses the idea of light particles traveling in waves to describe how all matter travels. Classical Mechanics vs. Quantum Mechanics --Classical deals with describing the motion of large bodies and quantum describes the motion of subatomic particles and atoms as waves. --Heisenberg = can’t find the exact velocity and position of a particle at the same time (like electrons) --Why? Because the mass is so small that when struck by a photon it affects its motion in a way that is not predictable. Therefore, just trying to determine the position changes its velocity!