update practice exams

diff --git a/physics/light-matter.md b/physics/light-matter.md
index 6630fd3f1bfe20f57f5d7c6eb9dbbd5c635632ed..ce114bac8b0daeddb34a5c65ac2b632fb06d4adb 100644 (file)
--- a/physics/light-matter.md
+++ b/physics/light-matter.md
@@ -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
 
@@ -68,9 +69,13 @@ $f$ is frequency of incident photon (**not** emitted electron)
 $\phi$ 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