#### Wave / particle (quantum) models
wave model:
+
- cannot explain photoelectric effect
- $f$ is irrelevant to photocurrent
- predicts that there should be a delay between incidence of radiation and ejection of e-
particle model:
+
- explains photoelectric effect
- rate of photoelectron release is proportional to intensity of incident light
- shining light on a metal "bombards" it with photons
## Quantum mechanics
+- uncertainty occurs in any measurement
+- inherent physical limit to absolute accuracy of measurements (result of wave-particle duality)
+- interaction between observer and object
+- measuring location of an e- requires hitting it with a photon, but this causes $\rho$ to be transferred to electron, moving it
+
+### Indeterminancy principle
+
+$$\sigma E \sigma t \ge {h \over 4 \pi}$$
+
+where $\sigma n$ is the uncertainty of $n$
+
+**$\sigma E$ and $\sigma t$ are inversely proportional$**
+
+Therefore, position and velocity cannot simultaneously be known with 100% certainty.
+
+### Single-slit diffraction
+
+- one photon passes through slit at any time (controlled by intensity)
+- diffraction pattern can be explained by wave front split into wavelets
+- diffraction can be represented as uncertainty of photonic momentum
+
+
+### Comparison with Bohr's model
+
+**Newtonian (deterministic) model** - current $x$ and $v$ are known, so future $x$ can be calculated
+
+**Quantum mechanical model** - electron clouds rather than discrete shells (electrons are not particlces). We can only calculate probability of an electron being observed at a particular position
+
774 abc melbourne
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