Chemistry: Electromagnetic Radiation & Line Spectra

Pre-College Issues High School Life
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<p>We are doing this in Chemistry and I don't really understand it. If anyone here can give me a general idea of the subject that'll be nice. Anything is REALLY helpful.</p>

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<p>A wave is defined as a vibrating disturbance that transmits energy. </p>

<p>Look at this picture:
<a href=“http://www.kss.sd23.bc.ca/staff/jstracha/physics_11/course_material/unit7/U07L01/wave_amp.JPG[/url]”>http://www.kss.sd23.bc.ca/staff/jstracha/physics_11/course_material/unit7/U07L01/wave_amp.JPG&lt;/a&gt;
The amplitude is the distance from the middle of the wave to a peak (crest) or trough. The wavelength is the distance (in meters) between a point on a wave and another point of identical amplitude right next the first point. The frequency, given by the letter nu (sometimes people are lazy and use the letter v), is the number of waves that pass through a point per second (in hertz).</p>

<p>The speed of a wave is its frequency times wavelength.</p>

<p>Electromagnetic waves have electric and magnetic field components as seen here:
<a href=“http://micro.magnet.fsu.edu/primer/java/wavebasics/basicwavesjavafigure1.jpg[/url]”>http://micro.magnet.fsu.edu/primer/java/wavebasics/basicwavesjavafigure1.jpg&lt;/a&gt;
Both components have the same wavelength, frequency, and amplitude, and are in perpendicular planes. This model, proposed by James Maxwell, explains the behavior of light.</p>

<p>Electromagnetic waves travel at about 3.00 x 10^8 meters per second (depending on medium). This is important for calculations, where this speed is denoted as c (the speed of light). So if you’re given the frequency and are asked to find the wavelength you can using the formula c = frequency times wavelength.
This picture shows common forms of electromagnetic radiation. Note that as the wavelength gets shorter, the frequency gets higher. Humans are able see the small subset of electromagnetic radiation known as visible light. We see different frequencies as different colors.
<a href=“http://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/EM_spectrum.svg/1000px-EM_spectrum.svg.png[/url]”>http://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/EM_spectrum.svg/1000px-EM_spectrum.svg.png&lt;/a&gt;&lt;/p&gt;

<p>…</p>

<p>When energized, atoms emit radiation at particular wavelengths - these are known as line spectra. Different elements have different spectra (this is how we can tell what stars are made of).
A model proposed by Niels Bohr explains (kind of) line spectra. He thought that electrons can only circle around nuclei of atoms in certain particular orbits. When the electrons are in the lowest orbits possible, the atom is in what is called the ground state. If an electron jumps to a higher orbit (by an input of energy), the atom is “excited.” When excited electrons return to their ground state, they have to release the energy as a photon. The photons we see are the line spectra.
If you need to calculate stuff google the “rydberg formula” (or look in your textbook)</p>

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<p>A very interesting application of line spectra comes in the form of spectral lines, that is, holes in a continuous spectrum of light that come from stars. You can develop models predicting where the “holes” or lines will appear by using Bohr models of atoms (this works best with Hydrogen). </p>

<p>Basically, because atoms and molecules have electrons that occupy quantized “positions”, i.e., energy levels, they can only shoot out (or absorb) photons that correspond to jumps between these quantized energy levels. </p>

<p>I’m not sure exactly what information you’re looking for, though. Do you have any specific questions?</p>

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<p>@aldfig0 That really helped thank you so much. One other question. If some elements produce bright light line spectra, what produces a continuous spectra? I got question wrong on a worksheet my class did in class.</p>