wave nature of light

beam of electrons fired two narrow slits - electron diffraction

Exhibit a diffraction pattern.

Like a light wave not a particle beam.

1 e- at a time still exhibits a diffraction pattern.

Unobserved electrons go through both slits at the same time

One electron interferes with itself.

When observed at the detector one electron strikes the detector at different places, filling out the diffraction pattern over several thousand measurements.  

De Broglie wavelength

a single e- traveling through space has a wave nature

• wavelength is related to its KE and thus its velocity

• higher the velocity the higher the frequency and the shorter the wavelength

the uncertainty priniciple

When we watch the detector array, the e^- goes through both slits and we get an interference pattern → Wave Behavior.

We can place a laser right behind the slits we will get a flash denoting which slit the electron goes through.

When we measure at the slit the e^- only goes through one slit and the diffraction pattern disappears → Particle Behavior.

Wave behavior and particle behavior are complementary properties, that is, they are mutually exclusive.

Heisenberg’s uncertainty principle

an electrons velocity is related to its wave nature and its position is related to its particle nature. Therefore we cannot measure an electrons velocity and position at the same time with infinite precision

in other words, an electrons velocity and position are complementary

Indeterminacy

Classical Newtonian physics is deterministic – if you know the position and velocity vector of an object you can determine exactly where it will be at some future point in time.

Quantum Mechanics is indeterministic – if you know the position and velocity vector of an object you cannot determine exactly where it will be at some future point in time but you can determine a group of locations that it be and a statistical probability of it being there.

Here we have a probability distribution map instead of a trajectory.