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7 - Modern Physics
| Quantum Effects | | Atomic Physics | | Nuclear Physics | | Elementary Particles | | Relativity |
7A - Quantum Effects7A10 - Photoelectric Effect | Photoelectric Effect with Electroscope (7A10.10)
Bright white light from a carbon arc lamp strikes a metal plate mounted on a negatively charged electroscope. The electroscope discharges quickly if the plate is zinc, slower for aluminum or copper. Will not discharge if a plate of glass is held between the light and the zinc (cuts out UV), or if the electroscope is positively charged. |
| Photomultiplier Tube
A show and tell item. |
| Solar Cells (7A10.40)
Use a bright light to power a small motor. |
7A15 - Millikan Oil Drop | Millikan Oil Drop (7A15.10)
Oil drops suspended between charged parallel plates (qualitative only). |
| Millikan Oil Drop Model (7A15.25)
Two parallel metal plates are connected to a Wimshurst machine with a pith ball connected to the bottom plate. As the machine is cranked, the electric field increases and eventually the force on the pith ball will overcome the force of gravity and it will levitate between the plates. Note: This uses the same setup as the Bouncing Ping Pong Balls (5B10.30). |
7A50 - Wave Mechanics | Microwave Barrier Penetration (7A50.20)
Microwaves are totally internally reflected in an acrylic prism, with no transmission through the apparatus to a detector. If a second prism is brought close, but not touching, the incident microwaves can penetrate through the air gap into the detector. |
| Vibrating Circular Wire (7A50.40)
A 10" diameter loop of thin wire is attached to a speaker driver and driven at frequencies that set up standing waves in the loop. Useful for talking about de Broglie waves. |
7A55 - Particle/Wave Duality | Particle in a Box
A particle in a box. |
7A60 - X-ray and Electron Diffraction | Electron Diffraction (7A60.10)
Electrons are diffracted through a thin polycrystalline graphite mesh (Debye-Scherrer diffraction) and hit a fluorescent screen. The diffraction pattern consists of a central bright spot of undeflected electrons and two concentric rings. The diameters of the rings can be changed by altering the accelerating voltage of the electrons (increasing the momentum decreases the de Broglie wavelength). |
| Optical Analog of X-ray Diffraction from DNA (7A60.25)
A Helium-Neon laser beam is diffracted by the spring from a ball point pen. The resulting pattern shows the same characteristics of diffraction from a double helix including missing orders. |
| Bragg Diffraction of Microwaves (7A60.50)
Microwaves are diffracted by a 3D lattice of aluminum cylinders. Both the detector and crystal are rotated appropriately to observe minima and maxima. |
| Sample X-ray Tubes (7A60.95)
Various commercial and specialty X-ray tubes. |
7A70 - Condensed Matter | Flux Pinning (7A70.25)
A large YBCO superconductor similar to 5G50.50, except specially designed to show flux pinning. When cold, the superconductor will levitate above strong permanent magnets, or remain suspended underneath. |
7B - Atomic Physics7B10 - Spectra | Line Spectra (7B10.10)
An incandescent bulb and spectral tubes of hydrogen, neon, mercury, and helium are arranged in a vertical stack. Transmission gratings are passed out to the class to compare a continuous spectrum and individual emission spectra. |
| Hydrogen Spectrum
Just a single hydrogen spectral tube and diffraction gratings. |
7B11 - Absorption | Absorption by Sodium Vapor (7B11.25)
A large salt flame is placed in front of an incandescent light and a sodium light. The flame looks normal with the white light, but appears dark in front of the sodium light. |
| Absorption Spectrum of Neophan Glass (7B11.40)
A piece of neophan glass inserted into a continuous spectrum demonstrates broad absorption bands in the yellow and green; used by glass blowers to cut out sodium glare. |
7B13 - Resonance Radiation | Ultraviolet in the Spectrum (7B13.40)
Light from a carbon arc lamp is spread into a continuous spectrum. A fluorescent sheet is placed in the ultraviolet and fluoresces where no visible light exists. Note: This is done on the same setup as Infrared in the Spectrum (6B40.41). |
| Fluorescence and Phosphorescence (7B13.51)
Fluorescent materials viewed under ultraviolet light including minerals, paints, dyes, and uranium glass. |
| Luminescence and Chemiluminsecence (7B13.55)
Luminescent plastics are held in front of an ultraviolet light and then glow in the dark. Chemiluminescence: a chemical glow stick that emits light when the chemicals mix. |
7B30 - Ionization Potential | Frank-Hertz Experiment (7B30.20)
An experiment demonstrating quantized energy levels of bound electrons in mercury. A voltage/current curve for accelerated electrons through mercury vapor is displayed on the oscilloscope and seen to contain repetitive peaks and valleys (where the electrons are absorbed by the mercury). |
7B35 - Electron Properties | Discharge Tube and Vacuum Pump (7B35.10)
An electric current through a long glass tube as it is being evacuated. The glow from the current goes from nothing at atmospheric pressure to a maximum at low pressure and finally back to nothing when the tube is fully evacuated. At the proper pressure level, a structured discharge is seen. |
| Crooke's Tube with Maltese Cross (7B35.40)
An electron beam produces a shadow of a Maltese cross on a fluorescent screen. |
| Crooke's Tube with Paddle Wheel (7B35.50)
A small paddlewheel is free to roll along the axis of a Crooke's Tube. When current is flowing through the tube, electrons strike the paddles and heat the gas slightly behind the paddle, causing it to rotate in the direction of electron flow. This is similar to the Crooke's Radiometer (4D20.10). |
| Plasma Tube (7B35.75)
An evacuated tube containing a metal conductor is energized by a Tesla coil and forms long flickering streamers of current which are attracted to fingers touching the outside of the tube. |
7D - Nuclear Physics7D10 - Radioactivity | Geiger Counter (7D10.10)
A Geiger counter detects beta and gamma radiation. Several radioactive sources are available. Probe and source can be put in a special frame which allows the distance between them to be varied to determine the effect on count rates. Absorbers of different materials fit in slots in the frame to demonstrate their shielding effects. |
7D30 - Particle Detectors
7D50 - Models of the Nucleus | Rutherford Scattering Model (7D50.10)
An analogue of Rutherford's alpha scattering experiment has rolling ball bearings which strike a "nucleus" and scatter at various angles. |
7F - Relativity7F10 - Special Relativity | Streib's Relativity Machine (7F10.10)
Status: Unavailable
A device which simulates length and time contraction at relativistic speeds. |
| Length Contraction Board (7F10.32)
Show and tell item with boards of different lengths to display the Lorentz contraction at 0, .9c, .99c, .999c, etc. |
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