refine light & matter cheatsheet

diff --git a/physics/light-matter-ref.md b/physics/light-matter-ref.md
index 170d6a4727a09a831458353a3db0a148a3d15d3e..c0488911067fbce8879b371a6c15bffb4b2b6fd4 100644 (file)
--- a/physics/light-matter-ref.md
+++ b/physics/light-matter-ref.md
@@ -16,7 +16,9 @@ $$f={c \over \lambda}$$
 
 $$E=hf={hc \over \lambda}$$
 
-$$h=6.63 \times 10^{-34}\operatorname{J s}=4.12 \times 10^{-15} \operatorname{eV s}$$
+$$h=6.63 \times 10^{-34}\operatorname{J s}=4.14 \times 10^{-15} \operatorname{eV s}$$
+
+$$ 1 \operatorname{eV} = 1.6 \times 10^{-19} \operatorname{J}$$
 
 ## Force of electrons
 
@@ -28,6 +30,7 @@ $$F=evB$$
 - if $V_{\operatorname{supply}} > 0$, e- are attracted to collector anode
 - if $V_{\operatorname{supply}} < 0$, e- are attracted to illuminated cathode, and $I\rightarrow 0$
 - $v$ of e- depends on ionisation energy (shell)
+- max current depends on intensity
 
 ### Threshold frequency
 - *threshold frequency* $f_0$ - minimum frequency for photoelectrons to be ejected
@@ -45,13 +48,15 @@ $$\phi=hf_0$$
 
 $$E_{\operatorname{k-max}}=hf - \phi$$
 
-voltage in circuit = max $E_K$ in eV
+voltage in circuit or stopping voltage = max $E_K$ in eV  
+equal to $x$-intercept of volts vs current graph (in eV)
 
 ### Stopping potential
 
 _Smallest voltage to achieve minimum current_
 
-$$V_0 = {E_{K \operatorname{max}} \over q_e} = {{hf - \phi} \over q_e}$$
+<!-- $$V_0 = {E_{K \operatorname{max}} \over q_e} = {{hf - \phi} \over q_e}$$ -->
+$$V=h_{\text{eV}}(f-f_0)$$
 
 ## De Broglie's theory