06-Spectra1 - [R1 James Dalessio 2010] 6. Spectra I -...

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[R1 James Dalessio 2010] 6. Spectra I - PreLab Name: Section: Date: Electro-Magnetic Waves Nerd-speak for light When we talk about light we usually assume we are talking about visible light, the type of light we see with our eyes. We know that visible light comes in many different colors. However, light also comes in many different colors we can't see. Below is a chart showing all of the different “colors” of light. Note that some textbooks refer to visible light as simply “light” and all types of light as Electro-Magnetic radiation. For light, “color” is just a measurement of the energy contained by each piece of light. Each piece of light is called a photon . For example, a blue photon would have more energy than an orange photon. Notice that Ultra-Violet, X-Rays, and Gamma Rays are all more energetic than visible light. This is why they are all harmful in large quantities. The low energy types of light are rather harmless, and often pass clear through our bodies with no effect. (think about all the radio waves that are passing through you right now, no need for a foil hat) When describing light, scientists often use the units of eV, or electron volts, as a unit of energy. Sometimes instead of energy, scientists will use wavelength or frequency to describe the color of light. Here are 4 different ways someone might describe a piece of light. ... The light is Yellowish-Green. Each photon has an energy of 2.25eV The light has a wavelength of 550nm (10^-9 meters) or 5500 A (10^-10 meters) The light has a frequency of 5.45E14 Hz Every one of these statements is identical. The color, energy, frequency, and wavelength of light are all one in the same.
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(2) Question 1: Which has more energy, a photon of Ultra-Violet light or a photon of Radio light? Daddy, where does light come from? Well little Jimmy, when two pieces of light really love each other . .. To understand how most visible light is created we have to understand Quantum Mechanics. I'll spare you the gory details, for they are rather complicated and strange. Lets just use a loose metaphor. Imagine you are leaning out the window of a skyscraper. If you were to drop a bowling ball from the 3 rd floor it would hit the ground really hard. If you dropped it from the 4 th floor, it would hit the ground even harder. The harder it hits, the more energy we say it had. In an atom, the electrons are pulled on by the nucleus, the same way the bowling ball is pulled towards the Earth. If an electron “falls” in closer to the nucleus it should gain energy, just like the bowling ball. However, due to Quantum Mechanics, the electron isn't allowed to gain any energy. So where does this energy go? It is released as light.
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This note was uploaded on 02/01/2012 for the course PHYS 133 taught by Professor Staff during the Fall '08 term at University of Delaware.

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06-Spectra1 - [R1 James Dalessio 2010] 6. Spectra I -...

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