Transcript Unit 4-3 Noteguide Phsyics and Quantem Mechanical

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!