From 9507a6eb168ce1668974742941f08cd2e328abfc Mon Sep 17 00:00:00 2001
From: Eugeniy Mikhailov <evgmik@gmail.com>
Date: Thu, 26 Sep 2013 13:59:43 -0400
Subject: pe-effect procedures rewritten

---
 pe-effect.tex | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

(limited to 'pe-effect.tex')

diff --git a/pe-effect.tex b/pe-effect.tex
index eb1dffb..d732579 100644
--- a/pe-effect.tex
+++ b/pe-effect.tex
@@ -114,19 +114,35 @@ the $h/e$ Apparatus.
 \begin{enumerate}
 \item Adjust the $h/e$ Apparatus so that one of the blue first order spectral lines falls upon the opening of the mask of the photodiode. 
 \item Press the instrument discharge button, release it, and observe how much time\footnote{Use the stopwatch feature of your cell phone? You don't need a precise measurement.} is required to achieve a stable voltage.
-\item Place the variable transmission filter in front of the white reflective mask (and over the colored filter, if one is used) so that the light passes through the section marked 100\% and reaches the photodiode. Record the DVM voltage reading in the table below.
-\item Do the exact same thing for another blue spectral line.
-\item It's important to check our data early on to make sure we are not off in crazyland. This procedure is technically known as ``sanity checking''. According to equation Eq.~\ref{eq:pe} the frequency (or, better, wavelength) of light can be found from the measured voltage with knowledge of the work function $\phi$. Unfortunately, we don't know the work function. You'll measure it in the second part of the lab. For now, compute $\Delta V_0$ between the two measurements and use it to compute $\Delta \lambda$ or $\Delta \nu$. Does your data agree with the accepted value?  For this computation, it might be helpful to realize that $eV_0$ is the electron charge times the voltage. If you measured $V_0=\unit[1]{V}$ then $eV_0 =1$ ``electron-volt'' or ``eV''.  This is why electron-volt units are useful. Also, $hc=\unit[1240]{nm~eV}$.
-\item Go back to the original spectral line.
-\item Move the Variable Transmission Filter so that the next section is directly in front of the incoming light. Record the new DVM reading, and time to recharge after the discharge button has been pressed and released.
-\item Move the Variable Transmission Filter so that the next section is
-directly in front of the incoming light. Record the new DVM reading and
-approximate time to recharge after the discharge button has been pressed and
-released.
 
-Repeat step 3 until you have tested all five sections of the filter.
+\item It's important to check our data early on to make sure we are not off
+	in crazyland. This procedure is technically known as ``sanity
+	checking''. According to equation Eq.~\ref{eq:pe} the frequency
+	(or, better, wavelength) of light can be found from the measured
+	voltage with knowledge of the work function $\phi$. Unfortunately,
+	we don't know the work function. 
+	You'll measure it in the second part of the lab. 
+\begin{itemize}
+	\item For now switch to violet color and measure the stopping
+		potential for this color.
+	
+	\item compute $h c$ using  $\Delta
+		V_0$ between the two measurements and  values of light wavelength for this
+		two cases.  Does your data agree with the accepted value?  For this
+		computation, it might be helpful to realize that $eV_0$ is the electron
+		charge times the voltage. If you measured $V_0=\unit[1]{V}$ then $eV_0 =1$
+		``electron-volt'' or ``eV''.  This is why electron-volt units are useful.
+		Also, $hc=\unit[1240]{nm~eV}$.
+\end{itemize}
 
-Repeat the procedure with a second color from the spectrum.
+\item Go back to the original spectral line.
+\item Place the variable transmission filter in front of the white
+	reflective mask (and over the colored filter, if one is used) so
+	that the light passes through the section marked 100\% and reaches
+	the photodiode. Record the DVM voltage reading and  time to
+	recharge after the discharge button has been pressed and released.
+\item Do above measurements for all sections of the variable transmission filter. 
+released.
 
 \end{enumerate}
 
-- 
cgit v1.2.3

