Merge: forgot some shit again

diff --combined physics/light-matter.md
index a2d5f6dfc60580a251e2eee8b3ce6b07a33daedb,6630fd3f1bfe20f57f5d7c6eb9dbbd5c635632ed..ce114bac8b0daeddb34a5c65ac2b632fb06d4adb
--- 1/physics/light-matter.md
--- 2/physics/light-matter.md
+++ b/physics/light-matter.md
@@@ -46,7 -46,6 +46,7 @@@ particle model
  - rate of photoelectron release is proportional to intensity of incident light
  - shining light on a metal "bombards" it with photons
  - no time delay
 +- one photon releases one electron
  
  #### Work function and threshold frequency
  
@@@ -69,13 -68,9 +69,13 @@@ $f$ is frequency of incident photon (**
  $\phi$ is work function ("latent" energy)
  
  Gradient of a frequency-energy graph is equal to $h$  
 -y-intercept is equal to $\phi$
 +y-intercept is equal to $\phi$  
 +voltage $V$ in circuit is indicative of max kinetic energy in eV
  
  #### Stopping potential $V_0$
 +
 +Smallest voltage to achieve minimum current
 +
  $$V_0 = {E_{K \operatorname{max}} \over q_e} = {{hf - \phi} \over q_e}$$
  
  ## Wave-particle duality
@@@ -110,7 -105,8 +110,8 @@@ $$\rho = {hf \over c} = {h \over \lambd
  
  
  ### Absorption
- - Black lines in spectrum show light not reflected  
+ - Black lines in spectrum show light not reflected
+ - Frequency of a photon emitted or absorbed can be calculated from energy difference: $E_2 – E_1 = hf$ or $= hc$
  
  ### Emission
  
@@@ -171,6 -167,17 +172,17 @@@ Therefore, position and velocity canno
  
  **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
  
+ Newton's and Einsteins models work together  
+ 
+ ### Photon-electron interaction
+ 
+ When a photon collides with an electron, momentum is transferred to electron.
+ 
+ $$\rho_{\text{photon}}={h \over \lambda}$$
+ $$E=\rho c$$
+ 
+ 
+ 
  
  
  774 abc melbourne