From: Andrew Lorimer <andrew@lorimer.id.au>
Date: Sun, 23 Sep 2018 12:30:15 +0000 (+1000)
Subject: add to cheatsheet
X-Git-Tag: yr11~35
X-Git-Url: https://git.lorimer.id.au/notes.git/diff_plain/9ff87d786756e73211dddee64edd240add4ba33f

add to cheatsheet
---

diff --git a/physics/final.pdf b/physics/final.pdf
index e027227..ae315fb 100644
Binary files a/physics/final.pdf and b/physics/final.pdf differ
diff --git a/physics/final.tex b/physics/final.tex
index 4fab03e..6e10af0 100644
--- a/physics/final.tex
+++ b/physics/final.tex
@@ -121,7 +121,7 @@
 
   $\text{elastic potential energy} = {1 \over 2}kx^2$
 
-  $x={2mg \over k}
+  $x={2mg \over k}$
 
 % -----------------------
   \subsection*{Motion equations}
@@ -243,7 +243,7 @@
 
     \[v=\sqrt{Gm_{\operatorname{planet}} \over r} = \sqrt{gr} = {{2 \pi r} \over T}\]
 
-    \[T={\sqrt{4 \pi^2 r^3} \over {GM}}\tag{period}\]
+    \[T={\sqrt{4 \pi^2 r^3} \over {GM_\text{planet}}}\tag{period}\]
 
     \[\sqrt[3]{{GMT^2}\over{4\pi^2}}\tag{radius}\]
 
@@ -278,7 +278,7 @@
     \[{V_p \over V_s}={N_p \over N_s}={I_s \over I_p} \tag{xfmr coil ratios} \]
 
     \textbf{Lenz's law:}  $I_{\operatorname{emf}}$ opposes $\Delta \Phi$ \\
-    % emf is gradient of flux-time graph
+    (emf creates $I$ with associated field that opposes $\Delta \phi$)
 
     \textbf{Eddy currents:} counter movement within a field
 
@@ -330,6 +330,7 @@
     \includegraphics[height=4cm]{graphics/dc-motor-2.png}
     \includegraphics[height=3cm]{graphics/ac-motor.png} \\
 
+    Force on current-carying wire, not copper \\
     $F=0$ for front & back of coil (parallel) \\
     Any angle $> 0$ will produce force \\
 % \end{wrapfigure}
@@ -363,17 +364,21 @@
 
   % -----------------------
   \subsection*{Doppler effect}
+
   When $P_1$ approaches $P_2$, each wave $w_n$ has slightly less distance to travel than $w_{n-1}$. $w_n$ reaches observer sooner than $w_{n-1}$ ("apparent" $\lambda$).
 
   % -----------------------
   \subsection*{Interference}
 
+  \textbf{Standing waves} - constructive int. at resonant freq
 
+  \textbf{Coherent } - identical frequency, phase, direction (ie strong & directional). e.g. laser
 
-  \textbf{Standing waves} - constructive int. at resonant freq
+  \textbf{Incoherent} - e.g. incandescent bulb
 
-  \subsection*{Harmonics}
 
+  % -----------------------
+  \subsection*{Harmonics}
 
   \(\lambda = {{al} \div n}\quad\) (\(\lambda\) for \(n^{th}\) harmonic)\\
   \(f = {nv \div al}\quad\) (\(f\) for \(n_{th}\) harmonic at length
@@ -397,6 +402,7 @@
     \(l\) = distance from source to observer\\
     \(d\) = separation between each wave source (e.g. slit) \(=S_1-S_2\)
     \item significant diffraction when ${\lambda \over \Delta x} \ge 1$
+    \item diffraction creates distortion (electron $>$ optical microscopes)
   \end{itemize}
 
 
@@ -448,23 +454,23 @@
 
   \textbf{Work function $\phi$}
 
-  Minimum $E$ required to release photoelectrons. Magnitude of $y$-intercept of frequency vs $E_K$ graph. $\phi$ is determined by strength of bonding.
+  Minimum $E$ required to release photoelectrons. Magnitude of $y$-intercept of $f$ vs $E_K$ graph. $\phi$ is determined by strength of bonding. Units: eV or J.
 
-   $\phi=hf_0$
+  $\phi=hf_0$
 
   \textbf{Kinetic energy}
 
   E_{\operatorname{k-max}}=hf - \phi
 
-  voltage in circuit or stopping voltage = max $E_K$ in eV
-  equal to $x$-intercept of volts vs current graph (in eV)
+  voltage in circuit or stopping voltage = max $E_K$ in eV \\
+  $E_K = x$-int of $V\cdot I$ graph (in eV) \\
+  dashed line below $E_K=0$ ($E_K < 0$ is impossible)
+
 
   \textbf{Stopping potential $V$ for min $I$}
 
   $V=h_{\text{eV}}(f-f_0)$
 
-  % \columnbreak
-
   \subsection*{De Broglie's theory}
 
   \[ \lambda = {h \over \rho} = {h \over mv} \]
@@ -542,19 +548,12 @@
   \textbf{Precision} - concordance of values \\
   \textbf{Accuracy} - closeness to actual value\\
   \textbf{Random errors} - unpredictable, reduced by more tests \\
-  \textbf{Systematic errors} - not reduced by more tests
-
-  \columnbreak
-
-  \quad
-
-
-
-
-
+  \textbf{Systematic errors} - not reduced by more tests \\
+  \textbf{Uncertainty} - margin of potential error \\
+  \textbf{Error} - actual difference \\
+  \textbf{Hypothesis} - can be tested experimentally \\
+  \textbf{Model} - evidence-based but indirect representation
 
 \end{multicols}
 
-% \includegraphics[height=5cm]{graphics/em-spectrum.png}
-
 \end{document}