small fixes

1 files changed, 17 insertions, 16 deletions

diff --git a/interferometry_new.tex b/interferometry_new.tex
index 5cacbe5..ec489fc 100644
--- a/interferometry_new.tex
+++ b/interferometry_new.tex
@@ -130,10 +130,11 @@ For each trial, approximately 50 fringes should be accurately counted and tabula
 %\noindent\textbf{\emph{Experimental tips}}:
 \subsection*{Experimental tips}
 \begin{enumerate}
+\item Make sure that all optical elements are bolted and cannot move if you bump them! It is good idea to tape the laser to the table.
 \item Avoid touching the face of the front-surface mirrors, the beam splitter, and any other optical elements!
 \item The person turning the micrometer should also do the counting of fringes. It can be easier to count them in bunches of 5 or 10 (\textit{i.e.} 100 fringes = 10 bunches of 10 fringes).
 \item Use a reference point or line and count fringes as they pass.
-\item  Before the initial position $X_1$ is read make sure that the micrometer has engaged the drive screw (There can be a problem with ``backlash''). Just turn it randomly before counting.
+\item  Before the initial position $X_1$ is read make sure that the micrometer has engaged the drive screw. Chose a direction in which you will move the micrometer handle and do a few turns in that direction prior counting, i.e. take a way the slack on a thread. If you decide to reverse the direction, remember there will be slack which you have to take off before micrometer engages. You will notice that fringes do not change until the slack is removed.
 \item  Avoid hitting the table which can cause a sudden jump in the number of fringes.
 \end{enumerate}
 
@@ -190,21 +191,6 @@ the following
 accepted experimental values: 
 Index of Refraction of Air(STP) = 1.000293 
 
-\begin{thebibliography}{99}
-
-
-\bibitem{mmoriginal}
-A.~A. Michelson,E.~W. Morley, ``On the Relative Motion of the Earth and the Luminiferous Ether,'' \emph{American Journal of Science} \textbf{34}(203), 333–345 (18870.
-
-\bibitem{MNtextbook}
-A.~C. Melissinos and J. Napolitano, \textit{Experiments in Modern Physics},
-(Academic Press, New York, 2003).
-
-
-\bibitem{indexref} \emph{Refractive index of air},  available at
-\url{https://emtoolbox.nist.gov/Wavelength/Documentation.asp}.
-
-\end{thebibliography}
 
 \newpage
 \section*{Observation of Gravitational Waves (LIGO)}
@@ -245,5 +231,20 @@ The space-time ripples cause the distance measured by a light beam to change as
 
 In 2015, LIGO observed the first direct detection of gravitational waves from the collision of two black holes.  Figure~\ref{LIGO_data.fig} shows data from the black hole merger event where the `strain' reflects the observed change in distance in the interferometer arm due to the passing gravitation wave, which oscillates as a function of time.  For a more information you can browse the \href{http://www.ligo.caltech.edu/}{LIGO webpage} and view a \href{https://www.ligo.caltech.edu/video/ligo20170601v2}{simulation of a black hole merger}.
 
+\begin{thebibliography}{99}
+
+
+\bibitem{mmoriginal}
+A.~A. Michelson,E.~W. Morley, ``On the Relative Motion of the Earth and the Luminiferous Ether,'' \emph{American Journal of Science} \textbf{34}(203), 333–345 (18870.
+
+\bibitem{MNtextbook}
+A.~C. Melissinos and J. Napolitano, \textit{Experiments in Modern Physics},
+(Academic Press, New York, 2003).
+
+
+\bibitem{indexref} \emph{Refractive index of air},  available at
+\url{https://emtoolbox.nist.gov/Wavelength/Documentation.asp}.
+
+\end{thebibliography}
 \end{document}