Beyond Labz

Overview

The primary purpose of the quantum simulation is to teach the concepts and fundamental principles that led to the development of atomic theory and eventually quantum mechanics. As is usually the case, these concepts and principles were discovered or elucidated by a series of experiments that were developed and carried out over a period of many years by some of the great minds of the 19^th and 20^th centuries. These experiments most often require extremely sophisticated equipment whose setup and operation is well beyond the scope of the Beyond Labz simulations.

In Beyond Labz: Quantum, these classic experiments (plus several others) are reproduced in a framework consistent with the other Beyond Labz simulations; that is, the student is put into a virtual environment where they are free to choose their equipment and build a conceptual experiment of their own design and then experience the resulting consequences. The focus in the quantum simulation is not how to use lasers, spectrometers, diodes, electron sources, and other pieces of equipment, but the focus is how each foundational experiment was conceptually conceived and realized and how the outcomes of these experiments were observed in the laboratory. The interpretation of these experiments and outcomes is the ultimate goal of these simulations and ties the concepts taught in the classroom with the great experimental work of the past.

In general, the simulated experiments in Beyond Labz: Quantum are based on the concept that a sample is probed with a source and then a detector of some kind is used to measure or detect any changes caused by the probe. In addition to the source, sample, and detector combination, a modifier can also be used to modify either the sample or the source. Not every experiment requires a source, a sample, or a modifier, but a detector must be used to detect a result or make an observation. The relative positions of the source, sample, and detector with each other are also an important component of the experimental design.

Given in the sections that follow are descriptions of the available sources, samples, detectors, and modifiers. Details on adjusting the settings on these devices and placing them on the optics table is given in the Laboratory section. Most of these devices have been highly idealized in order to simplify the simulation to within the general scope of the Beyond Labz series. A description of the degree of idealization for each device is also given.

Sources

Source	Description	Idealization
	Alpha Particles. This source provides a collimated beam of alpha particles (4He nuclei) with an energy of 5.4 MeV and an intensity of 105 particles per second. The source is turned on and off by opening and closing the cover.	The alpha particles are assumed to come from an 241Am source with a small aperture in front of the sample to collimate the beam. Experiments involving alpha particles should take place in a vacuum, but this is not shown in the simulation.
	Super Light Bulb.  This source provides light at all wavelengths from 20 nm up to as high as 20,000 nm with a uniform intensity. The intensity of the light can be selected at values of 1 nW, 1 µW, 1 mW, 1 W, 1 kW, and 1 MW. The super light bulb is turned on and off by clicking the green and red buttons.	Light sources do exist that provide light over a wide spectrum, but these sources cannot cover such a wide region of the electromagnetic spectrum nor do they provide light at a uniform intensity, thus the name for this source and the "virtual" look.
	Electron Gun. This source provides a collimated beam of electrons with selectable energies from 1 meV up to 50 keV and selectable intensities of 1 electron per second (e/s), 10 e/s, 100 e/s, 1000 e/s, 1 nA, 1 µA, 1 mA, and 1 A. The electron gun is turned on and off by clicking the green and red buttons.	An electron source does not exist that can produce a collimated beam of electrons over this range of energies and with a range of intensities from electrons per second up to amps. In addition, an actual laboratory experiment would require that these electrons be contained in a vacuum; otherwise, the electrons would ionize the air at high intensities and energies or collide with the air molecules at low intensities and be adsorbed.
	Laser. This source provides laser light at a single, selectable wavelength from 20 nm up to as long as 1 m with selectable intensities of 1 photon per second (p/s), 10 p/s, 100 p/s, 1000 p/s, 1 nW, 1 µW, 1 mW, 1 W, 1 kW, and 1 MW. The laser is turned on and off by clicking the green and red button.	Lasers do exist that can produce light over a range of wavelengths, but not even close to the range that this "virtual" laser can produce. The range of intensities covered by this laser is also significantly wider than what can be produced by a real laser. It should be noted, however, that the image used for this laser was modeled after an actual laser. The insides of this laser can be seen by hovering over the laser while it is on the optics table and turned off.

Samples

Samples	Description	Idealization
	Oil Mist. This is a conceptual oil mist chamber. Oil mist is provided by the atomizer outside the box, and the oil mist is allowed to fall through a small hole between the two plates. Another small hole (not shown) allows electrons to pass through the mist depositing electrons on the droplets. A telescopic eye piece is provided to see the oil droplets.	This oil mist chamber is only meant to be a conceptual image of the key features necessary for the Millikan oil drop experiment. There are several actual self-contained Millikan oil drop experiments that can be purchased and look significantly different from what is depicted here. The key ideas to remember here are that this chamber provides oil drops than can be viewed, allows electrons to be deposited on these drops, and allows an electric field to be applied.
	Liquids.  This is a cuvette used for holding liquid samples. There are 3 different types of liquids- Pure, Kinetics and Beer's Law.	There is no significant idealization done here except for the cuvette holder graphic. This graphic is an artist’s rendition of a cuvette holder that is consistent with the other graphic elements used in the simulation.
	Metal Foils. This is a device used for holding metal foils. The metal foils used in the simulation are 1 µm thick, and there are 41 metals that can be selected from the stockroom.	It is assumed in the simulation that all the metals can be rolled out into foils of 1 μm thick and in sufficient quantities to account for the size indicated in the graphic. Of course, many of the metals that can be selected in the simulation are (a) too reactive in air and cannot exist as shown on the optics table, (b) too rare and cannot be provided in quantities large enough to make the foils shown, or (c) too brittle and cannot be rolled out into foils.
	Gases. This is a cell used for holding gas samples. Ten different gases can be added by selecting from the stockroom.	There is no significant idealization done here except for the cell holder graphic. This graphic is an artist’s rendition of a cell holder that is consistent with the other graphic elements used in the simulation.
	Two Slit Device. This is a device used for adjusting the spacing of two infinitely narrow slits spaced as narrow as 1 nm wide up to 1 cm wide.	This device is fictional and does not exist in reality. An infinitely narrow slit is a limiting case with respect to the wavelength of the particle, and a device cannot be constructed that would adjust the slit spacings over such a wide range of values.

Detectors

The detectors used in the simulation are all fictional devices conceptually patterned after actual laboratory instruments. These types of detectors are actually used in the laboratory, but in this simulation they have been greatly simplified and idealized in order to focus on what they are detecting instead of how they are detecting it. The correct interpretation of a detector's output is the primary concern.

Brief descriptions of what each detector can measure and where they are useful are given in the following table. The graphic of each detector represents the detector on the optics table. Each detector is turned on and off in the simulation by clicking the red or green buttons. When a detector is turned on, a detector window is brought up that shows the detector output. Details on these detector windows are given in the Laboratory section.

Detector	Description
	Phosphor Screen. A phosphor screen is used to detect high-energy particles such as electrons or alpha particles. When a high-energy particle impacts the phosphor screen, the phosphor momentarily glows as a small spot at the position of impact. The brightness of a spot or area on the phosphor screen is a qualitative measure of the number of particles or intensity of the beam at that location. An actual phosphor screen is not an electronic device, but in the simulation it is treated as such in order to be consistent with the other detectors.
	Spectrometer.  A spectrometer is used to measure the intensity of light over a wide range of wavelengths. The spectrometer used here can operate at any necessary wavelength and plots the intensity of the detected light as a function of wavelength. The plotted intensity is expressed as a relative intensity from 0 to 1. The "relative" nature of the intensity changes depending on the experiment being performed. The display can be toggled from Intensity to Absorbance. The spectrometer cannot measure single photon events.
	Video Camera. An "everyday" video camera detects the wavelength and spatial location of photons as they strike the detector. In the simulation, of course, the video camera has been idealized to be able to detect photons of all wavelengths inside or outside the visible region. Essentially, the video camera and phosphor screen are similar in that they both detect the spatial locations of particles as they strike the detector except a phosphor screen detects electrons and alpha particles and a video camera detects photons. Both detectors indicate the intensity using brightness. The video camera can also measure the energy of photons in the visible region (the frequency) using color.
	Photodiode. A photodiode detects the integrated intensity of light over all wavelengths. That is, a photodiode is not wavelength specific but integrates the intensity of light over all wavelengths it can detect. In the simulation, the photodiode measures this intensity as a function of time. As with the spectrometer, the intensity is displayed as a relative intensity from 0 to 1.
	Bolometer. A bolometer is used to measure the energy and intensity of particles over a wide range of energies. The energies of these particles are measured in eV or in joules. The bolometer used here can detect electrons or alpha particles and plots the intensity of these particles as a function of energy. The plotted intensity is expressed as a relative intensity from 0 to 1. The “relative” nature of the intensity changes depending on the experiment being performed. The bolometer cannot measure single particle events. In most ways, the bolometer is equivalent to the spectrometer except it detects particles instead of photons.

Modifiers

The modifiers are used to apply electric or magnetic fields to the sample, used to heat up a sample, or placed before a detector to bend a particle beam. Again, the idea is to conceptually apply an electric field, or a magnetic field, or apply heat in order to observe a change with the detector. How these things are actually carried out in the laboratory is beyond the scope of this simulation. The following are descriptions of these modifiers.

Modifier	Description
	Electric Field. An electric field can be applied to a sample, or it can be placed on the optics table separate from the sample. How this will change the output on the detector will depend on the experiment. In nearly all cases, a DC field will be applied except in the case of a gas sample where an AC field is used. The type of field used is indicated on the LCD controller. The electric field can be placed in combination with a magnetic field. The maximum voltage that can be applied is 5000 V.
	Magnetic Field.  A magnetic field can be applied to a sample, or it can be placed on the optics table separate from the sample. How this will change the output on the detector will depend on the experiment. A uniform magnetic field is applied in all cases. The maximum field that can be applied is 100 T.
	Heat. The heat modifier will heat a sample to a maximum temperature of 4000 K. If the sample temperature is raised too high, then appropriate outcomes will occur. The heat modifier can only be applied to a sample.

Other idealizations

In the course of performing some of the experiments in Quantum lab, several other important idealizations or assumptions are made. The following is a list of some of the most important:

1. Most experiments involving light, especially in the visible region, require the room to be dark or the apparatus to be enclosed in order to avoid contamination from extraneous light sources. These types of precautions have not been taken in the simulation.
2. Experiments involving alpha particles and electrons, especially high energy and high intensity electrons require the experiment to be contained in a vacuum. This requirement is not shown in the simulation.
3. In the photoelectric and reverse photoelectric experiments, light or electrons strike a metal surface at an angle and give off electrons and photons, respectively. For the sake of simplicity, these electrons and photons come off the metal in a direction perpendicular to the incident beam and are collimated.
4. The emission spectra for HCl was generated by adding the individual atomic emission spectra for H and Cl. All other emission spectra were either measured or obtained from the NIST database.

Important Experimental Parameters

In order to quantitatively measure the charge-to-mass ratio of an electron (Thomson's experiment) and the charge on an electron (Millikan's oil drop experiment), several experimental parameters must be known that cannot be readily measured or determined in the simulation. These parameters and their values are given subsequently. 

Thomson's Experiment

Millikan's Oil Drop Experiment