Wave-Particle Duality Applications
Applying Wave-Particle Duality
Many applications utilize both wave-like and particle-like behaviors of EM radiation.
Eyeing Your Garage
The electric eye is an application of the photoelectric effect.
It uses photoelectrons emitted from a surface when struck by EM radiation of the correct frequency.
A photosensitive material is made into a photocell, which collects incoming light.
The photocell is placed in series in a circuit. When light strikes it, released photoelectrons make it a better conductor.
The current flow prevents a switch from triggering, which would open the circuit.
Garage doors use an emitter and electric eye combination near the bottom.
If something obstructs the beam, the photocell becomes a resistor, triggering the switch to open, stopping the door.
The emitter beam is usually in the infrared range.
The photoelectric material must trigger at the infrared range.
Garage doors may fail if the electric eye is overpowered by infrared from another source, such as direct sunlight.
Compton Funk
Collisions between electrons and photons and their conservation of momentum help reduce high-frequency waves from the sun.
The Compton effect: when an EM wave hits an electron, its wavelength changes slightly.
This change increases the wavelength and decreases the frequency of the wave.
This makes the EM wave safer, as it is less likely to cause cellular disruption.
This mostly happens as EM radiation travels through the sun's material.
Nuclear reactions occur deep in the sun's core, so EM radiation hits many particles along the way.
Instead of X-rays and gamma rays, lower-frequency, safer waves emerge.
The Earth’s atmosphere helps, but not nearly as much as the sun due to the lower particle density.
Spectra Man!
De Broglie’s matter wave equations for electrons can predict the atomic spectra of an atom.
Atomic spectra: EM wave emission from electrons excited to higher energy levels, then emitting EM waves when dropping back to the first level.
The larger the drop in energy level, the higher the EM radiation frequency emitted.
(energy is quantized and related to frequency).
Different-color emissions cause different atoms to produce different overall colors when heated or energized.
Each element has a unique set of atomic spectra, allowing matter identification.
Atomic spectra blend when viewed with the naked eye.
EM radiation diffracts; red light diffracts more due to longer wavelengths, and blue light diffracts less due to shorter wavelengths.
Spectroscope: a device using the wave-like nature of EM radiation to separate atomic spectra into separate color lines using a diffraction grating.
Diffraction grating: a transparent material with many small, lined deviations acting like optical slits.
Each color diffracts depending on frequency and wavelength.
Spectroscopes have a small opening to keep the device dark except the color pattern.
Spectrometer: a spectroscope set up to have wavelength-number measurements where the unique colors are seen.
Spectrometers and spectroscopes use the wave-like nature of EM radiation to split an element’s uniquely colored atomic spectra.
Atomic spectra are created based on the particle-like nature of EM radiation as well.
Spectrometers are used in astronomy, crime scene investigations, and film developing.
DVD
Digital video discs (DVDs) have small raised areas (pits) separated by a flat surface (land).
The surface is highly reflective and hit with a laser beam as it spins.
The raised points are thick enough to cause thin film interference, making the reflecting beam cause thin film interference.
A photocell produces a current when constructive interference occurs and no current when destructive interference occurs.
The electrical signal is conveyed as a series of “ons” and “offs” corresponding to the digital binary code of 1 and 0.
The data is processed for sound and/or video.
TEM and SEM
Electron microscopes use the wavelength of an electron.
Electrons have much smaller wavelengths, so electron microscopes can focus on objects that are much smaller and provide better detail and resolving power compared to light microscopes.
They use beams of electrons rather than light to study different materials, either across or through the sample.
The wavelength of electrons is so small that the images produced can be much more detailed than ones dervied by using light.
Transmission Electron Microscopes (TEM) send the beam through very thin sections of materials.
Scanning Electron Microscopes (SEM) reflect the electrons off the surface.
Both types of microscopes can produce images down to the atom size.