deletions | additions       diff --git a/section_EL2__.tex b/section_EL2__.tex  index aa3bd91..4f99d87 100644  --- a/section_EL2__.tex  +++ b/section_EL2__.tex 
...
\section*{EL2}  \subsection{Spectroscopy}  Under certain conditions, a substance will absorb or emit electromagnetic radiation in a characteristic way. Analysis of this can lead to identification of the substance.  \subsubsection{Absorption Spectra}  \begin{itemize}  \item Glowing stars emit all frequencies between UV and IR  \item Chromosphere contains ions, atoms, and small molecules  \item These absorb radiations  \item Emitted light is missing specific frequencies  \item Black lines on coloured backround correspond to particles in chromosphere  \end{itemize}  \subsubsection{Emission Spectra}  \begin{itemize}  \item Atoms/molecules/ions raised from ground state energy level when they absorb energy  \item Become excited  \item Lose energy by emitting EM radiation  \item Spectra of coloured lines on black backround  \end{itemize}  \subsection{Continuous and Atomic Spectra}  White light contains all visible wavelengths, and has a continuous spectra. Light from stars is not the same.  \subsubsection{Atomic Spectra of Hydrogen Atoms}  \begin{itemize}  \item Balmer in visible light  \item Lyman in UV light  \end{itemize}  Spectra are the result of the interaction of light and matter  \subsection{Bohr's theory and Wave-Particle Duality (WPD)}  \subsubsection{Wave Theory of Light}  \begin{itemize}  \item Light is a form of EMR, so has wavelength and frequency  \item Moves at the speed of light in a vacuum  \item Different colours have different wavelengths  \end{itemize}  \begin{equation*}  c=\lambda \times v  \end{equation*}  \subsubsection{Particle Theory of Light}  \begin{itemize}  \item Light is a stream of packets of energy  \item Photons  \end{itemize}  \begin{equation*}  E=h \times v  \end{equation*}  \subsubsection{Bohr's Theory}  \begin{itemize}  \item An excited atoms electrons will jump into higher energy levels  \item When they drop back, they emit EMR, giving an emission spectrum  \end{itemize}  When white light is passed through a cool sample of a gaseous element, black lines appear in the absorption spectrum. These correspond to the frequencies absorbed by the atoms in the sample. The intensities of these lines provide a measure of abundance.  \begin{itemize}  \item Explains Spectra  \item Relies on quantisation of energy  \item Electrons exist in definite levels/shells  \item A photon must be emitted when the electron drops  \end{itemize}  \subsection{Energy Levels and Quanta}  An electron can only possess definite amounts of energy; \textit{QUANTA}.  \begin{itemize}  \item Higher energy levels are further from the nucleus  \item Ground state is $n=1$  \end{itemize}