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General Quantum Physics

  • P2-01: PHOTOELECTRIC EFFECT AND PLANCK'S CONSTANT

    P2-01
    Demonstrate the frequency dependence of the photoelectric effect and determine the value of Planck's constant.
    This apparatus uses an intense broad-spectrum mercury lamp shining through filters of various frequencies to activate a photoelectric tube. A finely controlled DC power supply is used to create a stopping potential across the PE tube. By measuring the voltage required to stop electrons from being emitted by the photoelectric effect at different frequencies, we can work backwards to then calculate h/e.

    Allow the mercury lamp 5-10 minutes to warm up, then remove the covers from the lamp and the PE tube. For each frequency filter, adjust the input stopping voltage from the tunable power supply until the current measured on the the current amplifier reaches 0.

    Plot the five frequencies (c/wavelength) vs the voltage, and the slope should be h/e. By assuming a standard value for e, h can be computed, or vice versa.
    P2

    p2-01ap2-01bP2-01: PHOTOELECTRIC EFFECT AND PLANCK'S CONSTANT

     

  • P2-04 PHOTOELECTRIC PROPELLER

    P2-04
    Demonstrates solar cells
    Illuminating the solar cells with a 100 watt goose neck lamp runs the electric motor.
    P2, LS2

  • P2-05: PHOTO-RESISTOR RELAY

    P2-05
    Demonstrate operation of a photoresistor.

    A selenium photoresistor is in series with the coil in a relay circuit used to turn a light on and off. When no light shines on the selenium, it has a high resistance; however, as light falls on it the resistance falls. When the resistance is low the photoresistor passes current which turns on the relay. The light is connected in series with 110VAC through a normally open relay contact. Thus the light is made to go on and off because of the change in the resistance of the selenium due to an external light, which causes the relay to close or open.

    During the daylight, when a streetlight remains on, it is often due to pigeons despoiling the photocell, as illustrated in the photograph at the right above, where a piece of simulated pigeon poop has been positioned on the photocell, blocking the light.
    P2, LS2

    p2-05ap2-05b

  • P2-06 PHOTOELECTRIC TRUCK

    P2-06
    Demonstrates solar cells
    Shine a 100 watt goose neck lamp onto the photocell on top of the truck to make it start; remove the lamp to stop the truck.
    P2, LS2

  • P2-11: INTERFERENCE OF PHOTONS

    P2-11
    Demonstrate two-slit interference of single photons.

    Collimated light from a laser diode is incident on a double slit, creating interference. A photomultiplier tube sensitive to single photons is attached to the rotating telescope of the spectroscope opposite the light source. The signals from the tube are seen on the oscilloscope and heard using an audio amplifier and loudspeaker.

    As the photon counter is slowly rotated the intensity of photons traces out the interference pattern for the double slit used. An identical slide on the Laser Cart (Demonstration M1-11) can be used to display the double slit interference pattern.

    The double slit used has slit width of 0.04mm and slit spacing of 0.250mm. With the single photon counter you can hear about nine interference maxima in the main diffraction maximum, pass through the diffraction minima on either side, and hear a few interference maxima in the second diffraction maximum, as seen in the photograph above.
    P2, ME2, ME3

     

  • P2-12: X-RAY DIFFRACTION MODEL

    P2-12
    Show analog between diffraction of light by a two-dimensional grating and diffraction of x-rays by a single crystal.
    A laser beam is incident on a two-dimensional grating, resulting in a diffraction pattern which has the symmetry of the grating and is similar to the diffraction pattern of x-rays from a single crystal with that symmetry. A variety of optical crystals is available, as seen in the photographs above.

    p2-12ap2-12bp2-12c

  • P2-13: ELECTRON DIFFRACTION

    P2-13
    Demonstrates the wave properties of electrons
    Electrons are emitted by the cathode at the back end of the tube, are accelerated by a high voltage and strike a target of powdered graphite crystals, producing a characteristic circular diffraction pattern. The pattern can be seen when the diffracted electrons strike a phosphorescent coating at the front end of the tube. As the accelerating voltage is increased, decreasing the wavelength of the electrons, the circles become smaller. Quantitatively, the radius of the circle can be measured to be proportional to the wavelength, which is approximately inversely proportional to the square root of the kinetic energy.
    P2

  • P2-14: ELECTRON DIFFRACTION MODEL

    P2-14
    Analog to diffraction of electrons or x-rays by a powdered crystal.
    The laser creates a diffraction pattern of a wire mesh, a series of dots forming a square array. If the mesh is rotated a few times per second circles are formed, representing the random orientation of a powdered crystal target. Circles with the lowest combined order number are brighter. Note that in the picture, due to the short exposure time only segments of each circle are seen. Because your eye has a longer exposure time complete circles are seen.

    p2-14a

  • P2-15: WAVE PACKETS - OSCILLATORS

    P2-15
    Show that wave packets begin to form when sinusoidal oscillations with similar frequencies are combined.
    This is a generalization of the familiar beats experiment. Tune one of the oscillators to 500 Hertz, then tune the others to 499 Hertz and 501 Hertz using beats. When the third oscillator is added, notice that some of the beat envelopes are enhanced and others are inhibited.
    ME2, ME3
     

  • P2-20: FLUORESCENCE WITH LASER AND PYLON

    P2-20
    Demonstrates change in light color due to flourescence
    A green laser is pointed at an orange pylon, and the reflected light is seen to be a yellow color.
    OS12, ofc

  • P2-22 BICHSEL BOXES - BLACK BODY RADIATION

    P2-22
    Demonstrates Kirchoff's law of radiation
    The two holes appear equally dark, although the inside of one box is painted white and the other is painted black. The radiation emerging from the holes is a function only of temperature.
    P2

     

     

  • P2-24: GIANT-LIGHT BULB

    P2-24
    Demonstrate color and intensity changes of blackbody radiation with temperature.
    The giant (1500-Watt) light bulb is connected to a transformer. With a low current, the filament is dim and orange. As the current is increased, the filament is seen to get brigher and whiter.
    P2

    p2-24ap2-24b

  • P2-31: E/M OF ELECTRON

    P2-31
    Demonstrate that the charge and the mass of electrons are quantized.
    This is the classic lab apparatus. Electrons ejected from a hot filament are accelerated by a DC voltage and bent in circles by the magnetic field of a large pair of Helmholtz coils. The path of the electrons, shown in the photograph at the right, is visible due to interaction of the electron beam with residual nitrogen gas in the tube, which produces the characteristic blue glow.
    General Quantum Physics

    p2-31a

  • P2-41: POTENTIAL WELL - HILL TRACK MODEL

    P2-41
    Illustrate the concept of a quantum mechanical potential well.
    The hill track is treated as a potential well. The behavior of the ball in the well can be observed for various values of total energy.

  • P2-42: PARTICLE IN A BOX - 1D - QM INTRODUCTION

    P2-42
    Model behavior of a quantum mechanical one-dimensional particle in a box.
    The glider bounces back and forth on the air track modeling the behavior of a quantum mechanical particle in a box with infinitely high walls.

  • P2-43: CLASSICAL HARMONIC OSCILLATOR - QM INTRODUCTION

    P2-43
    Demonstrate the simple behavior of a classical particle moving in a quadratic field.
    Useful for demonstrating elementary properties of the motion, including turning points, the independence of amplitude and frequency, and visualizing the probability of finding the particle at different positions.

  • P2-51: OPTICAL ANALOG OF QM STATES AND OPERATORS

    P2-51
    Use properties of optical devices as analogs to illustrate quantum mechanical states and operators.
    Optical elements formed from polaroids, quarter and half wave plates, and combinations thereof, are analogous to spin up and spin down vectors and basis vectors formed from linear combinations of these vectors, the Pauli spin matrices, and the identity matrix. Place the blocks in the proper order and look through (or shine a light through) to observe zero, unity, or partial overlap of integrals. An accompanying document shows what is in the little cubes and how they work.

  • P2-61: DIRAC STRING TRICK

    P2-61
    Illustration of a topological property of the group of rotations.

    If the plate with hbar written on it is rotated by 360o the strings cannot be unwound without rotating the plate, but with a 720o rotation the strings CAN be unwound without rotating the plate. Each point along the string represents some rotation, the two ends being the identity (no rotation). Therefore this device illustrates the fact that a one-parameter sequence of rotations beginning and ending with the identity cannot be continuously deformed to the identity if the total rotation angle is 360o, but can be so deformed if the total angle is 720o. (The rotation group is thus said to be "doubly connected".) This property plays a role in the quantum mechanics of an object with half-integer spin: the quantum state vector of such an object is brought back to its negative after a 360o rotation, and back to itself only after a 720o rotation.

    A good description and animation can be found here: http://www.gregegan.net/APPLETS/21/21.html

    P2