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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 interacts with matter, it acts like particles. In this case, a single unit of EMR is called a photon.
Photons: Massless, point-like, individual "packets" of energy, The energy in a photon is correlated with its wavelength and frequency. This infers that light is quantized and not a continuous stream of energy.
When photons travel through space, their positions are probabilistic until measured.
Physicist Heisenberg stated that you cannot simultaneously know both the exact position and exact momentum of a particle. Accurately knowing one will decrease the accuracy of the other.
Physicist De Broglie stated that all quantum particles (e.g. protons, electrons, photons) behave like waves. Particles with less mass have larger "Broglie wavelength" (different from EMR wavelengths), which means their position is more probabilistic. This also means that more massive objects exhibit shorter Broglie wavelengths and therefore are less probabilistic in position.
Wavelength: As photons travel, their electric and magnetic fields oscillate in magnitude. These oscillations create measurable peaks and troughs in field strength. The distance between two points in space that peak in field strength is called wavelength, 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.
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
Radio: Minimal interaction with matter due to low energy and long wavelengths. Better for transmitting information across vast distances.
Microwaves: The magnetic fields that microwaves generate rotate polar molecules, creating heat.
Infrared: The frequency of the oscillating fields resonates with chemical bonds, which vibrate them. This also causes heat.
Visible and Longwave UV: The energy carried by visible and UV light is enough to excite electrons into a higher principal energy level.
Shortwave 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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