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Simple Explanation:
Electromagnetic Radiation
Electromagnetic radiation (EMR) is energy that travels though space, oscillating electric and magnetic fields wherever it travels through. It exhibits properties of both waves and particles, a phenomenon known as wave-particle duality.
When EMR travels through 3-dimensional space, it acts like a wave. Therefore, we can measure it by:
Wavelength: As the radiation travels through space, it creates disturbances in the electric and magnetic fields wherever it goes. This generates measurable peaks and troughs in energy level within these fields, and the distance of between peaks or troughs can be measured in meters.
Frequency: How much an electromagnetic wave oscillates in a second, measured in hertz. Inversely related to wavelength.
Speed: According to Einstein, the speed of EMR is constant. Therefore, we symbolize it as c in equations to substitute its constant speed: approximately 3.0 × 10⁸ m/s.
When EMR interacts with matter, it acts like particles. In this case, a single unit of EMR is called a photon.
Photons: Massless, individual "packets" of energy, Photons are quantized, which means that the energy in a photon is correlated with its wavelength and frequency.
Using Formulas to Interpret Photons
Formula One: c = λv
c: Speed of Light/EMR (3.0 × 10⁸ m/s)
λ (Lambda): Wavelength (m)
v: Frequency (s⁻¹)
This formula ties the relationships of speed, wavelength, and frequency together.
Formula Two: E = hv
E: Energy (J)
h: Planck’s Constant (6.626 × 10⁻³⁴ J·s)
v: Frequency (s⁻¹)
This formula implies that photons are quantized by tying the relationship of frequency and energy together.
Since v appears in both formulas above, we can combine the two formulas into: E = h(c/λ)
How EMR Interacts with Matter
Microwaves: The magnetic fields that microwaves generate rotate polar molecules, creating heat.
Infrared Light: The frequency of the oscillating fields resonates with chemical bonds, which vibrate them. This also causes heat.
Visible and UV Light: The energy carried by visible and UV light is enough to excite electrons into a higher principle energy level.
UV, X-Ray, and Gamma: The energy carried by these three categories of EMR are enough to ionize matter by launching electrons off orbit.
Excited States and Spectroscopy
As shown by Niels Bohr with his "planetary" model of the atom, when an electron absorbs energy, it can move from the ground state to a higher energy level, going into an excited state. However, this excited state is unstable, and the electron will eventually release the absorbed energy as photons as it returns to a lower energy level.
The photons released during this process have specific wavelengths that correlate with the energy differences between the electron's energy levels, which makes up an emission spectrum. The pattern of these wavelengths is unique to each atom or molecule due to their distinct electron configurations.
This should not be confused with the absorption spectrum, which displays the specific wavelengths of light that a substance absorbs to excite its electrons.
Interactive Simulation: Flame Lab
Instructions:
1. SAFETY!
2. Hold down your mouse and use the rod to grab a salt sample.
3. Insert the sample into the Bunsen torch flame to observe the color change.
Explanation: The fire provides the energy to excite electrons in the ions. The electrons then return to their ground state, releasing photons with specific wavelengths that color the fire.
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