QUANTUM MECHANICS

wave-like particles

All matter has ________ particles

particle-wave duality

this concept states that waves can exhibit particle-like properties while particles can exhibit wave-like properties.

probabilistic manner

particle-waves are described in a __________

probability distribution

the electron doesn't whiz around the nucleus, it has a __________ where it might be found

probability

the wave function associated with a particle only gives the ________ of finding the particle at a certain location in space, not a definite position

can't know both simultaneously

Some properties come in dual packages: you __________________ to arbitrary precision

Heisenberg Uncertainty Principle

it is impossible to know exactly both the velocity and the position of a particle at the same time

time

Example pairs of dual packages:

position: momentum

energy: ______

measurement

the act of "________" fundamentally alters the system

entanglement

information exchange alters a particle's state

entanglement

a phenomenon which exhibits correlations that cannot be explained by classical physics

for example:

When two particles, such as a pair of photons or electrons, become _____, they remain connected even when separated by vast distances

the particles go to other positions (uncertainty of momentum increases)

In the example of Heisenberg's Uncertainty Principle where the smaller the slit for light to pass through showcased light with larger dimensions:

when the uncertainty of position decreases, it breaks the equation, what happens to the particles to keep the principle real?

In classical physics, electrons orbit around the nucleus

But since Electrons exist as wave-like functions, the electromagnetic force (due to wiggling as the elctron accelerates) keeps the electrons in stable orbitals around the nucleus, preventing them from collapsing inwards and causing the atom to disintegrate

(it is the balance in kinetic and potential energy that allows it to stay stable, so a loss in energy would cause a prompt decay of orbit)

Why don't atoms disintegrate in nanoseconds?

They would melt or burn up before reaching a temperature hot enough for their blackbody radiation to peak in the UV

this means that its peak emission is in the infrared range, meaning it is not UV light that is emitted

infrared range is emitted as heat

- People encounter Infrared waves every day; the human eye cannot see it, but humans can detect it as heat. A remote control uses light waves just beyond the visible spectrum of light—infrared light waves—to change channels on your TV

Why don't hot objects emit more ultraviolet light than they do?

light quanta

Max Planck solved the "uv catastrophe" by postulating _______

because of its low frequency (long wavelength)

higher frequency radiation, shakes the electrons faster, knocking them out

Why was red light incapable of knocking electrons out of certain materials, no matter how bright?

•it was apparent that only a small set of optical frequencies (wavelengths) could be emitted or absorbed by atoms

What caused spectra of atoms to contain discrete "lines

fingerprint

each atom has a distinct "_______"

wavelengths

light only comes off at very specific ________, frequencies, or energies

true

TRUE OR FALSE

hydrogen, with only one electron and one proton, emits several wavelengths

•semiconductor devices

•computers, cell phones, etc.

•lasers

•CD/DVD players, bar-code scanners, surgical applications

•MRI (magnetic resonance imaging) technology

•nuclear reactors

•atomic clocks (e.g., GPS navigation)

Quantum Mechanics Contributions

No, the correspondence principle by Niel Bohrs tells us that quantum mechanics aim to explain the quantized level of the macro stuff that classical physics explain. So, it really aims to explain the small stuff in the same exact way classical physics explain the big stuff

Does the quantum mechanics or quantum physics contradict classical physics?

photons

light is quantized into packets called photons

6.63 x 10^ -34 J·s

planck's constant

2mm-4mm

On a sunny day outside where 10^15 photons per second enter our eyes, what is the diameter of our pupil?

6mm - 8 mm

On a moonlit night outside where 5 x 10^10 photons per second enter our eyes, what is the diameter of our pupil?

6mm pupil

On a moonless, clear, starry sky outside where 10^8 photons per second enter our eyes, what is the diameter of our pupil?

6.5

magnitude of the dimmest naked eye star

•1000 photons/sec entering eye

1/8 of a second = 100 photons entering

Light from dimmest naked eye star (mag 6.5):

interaction

the process of measurement involves

velocity

since the more precisely we want to know where something is, the harder it is to measure, we must anavoidably alter the _______ of the particle under study, thus changing its momentum

surface area of a sphere (4πr²) and in the solid angle subtended by a sphere (4π steradians)

In the context of quantum mechanics, 2π appears in the Heisenberg uncertainty principle (relating position and momentum) and in the reduced Planck constant (hbar), while 4π appears in the ______

diffraction

light emerging from a tiny hole or slit will diverge

momentum

We know its position very well (in at least one dimension) so we give up knowledge of _______ in that dimension—thus the spread

large opening

greater position uncertainty

results in smaller

momentum uncertainty,

which translates to less

of a spread angle

small opening

less position uncertainty

results in larger

momentum uncertainty,

which translates to more

of a spread angle

•Squint and things get fuzzy

- opposite behavior from particle-based pinhole camera

•Eye floaters

- look at bright, uniform source through tiniest pinhole you can make—you'll see slowly moving specks with rings around them—diffraction rings

•Shadow between thumb and forefinger

- appears to connect before actual touch

•Streaked street-lights through windshield

- point toward center of wiper arc: diffraction grating formed by micro-grooves in windshield from wipers

- same as color/streaks off CD

diffraction in our everyday world

The pattern on the screen showcase an interference pattern characteristic of waves, so light is a wave and not particulate

But if we focus on one photon at a time, we notice how the photons only land on the interference peaks

it is a non-intuitive combination of wavelike and particle like

- it appears to behave like waves but with low intensity, the photons arrive one at a time

What does the double slit experiment tell us?

impossible

it is ________ to simultaneously observe interference and know which slit the photon came through

interference pattern

If we try to detect which slit a photon passes through, the__________ disappears, and we see two distinct bands—suggesting the photons act like particles rather than waves.