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PHYS104

  • K7-21: RLC CIRCUIT - 10 KHZ - RESONANCE

    K7-21
    Demonstrate resonance in an RLC circuit.
    Using the circuit above, the frequency of the oscillator is swept to find the resonance. Both the signal from the oscillator and the signal across the resistor are displayed on the dual trace scope. The capacitor (0-300 picofarads) and the resistor (0-100 kilohms) in the circuit box are variable. The increase in amplitude of the signal across the resistor and the phase shift at resonance are both easily seen.
    K7, ME2, ME3

  • K8-01 ELECTROMAGNETIC WAVE - MODEL

    K8-01
    Shows the relationship between the electric and magnetic field vectors in a plane-polarized traveling electromagnetic wave
    Red pegs represent the electric field vector and blue pegs represent the magnetic vector. The spatial relationship between these vectors and the direction of propagation can be seen. By moving the model along its axis the temporal aspect of the wave can be shown. This wave has a wavelength of 0.81 meters, and as an EM wave would have a frequency of 370MHz
    FS1

  • K8-42: RADIOWAVES - ENERGY AND DIPOLE PATTERN

    K8-42
    Demonstrates transmission of energy in electromagnetic waves. Shows the radiation pattern of the dipole antenna

    This demonstration is centered on a simple radio transmitter with an antenna, which sends a signal to a handheld dipole antenna connected to a light bulb. The receiving antenna can be moved around in space, keeping the two antennas parallel, to observe the dipole radiation pattern. Rotating the receiving antenna to a vertical orientation shows that the radiowaves are polarized, as seen by the light going out.
    Background

    An antenna receives an induced current from the electromagnetic field of the passing wave. The dipole is a linearly polarized antenna, sensitive to signals oriented in a particular direction. In this experiment, we can see this dramatically, as changing the orientation of the antenna relative to the source produces a significant drop in signal strength, so that it is no longer receiving sufficient energy to light the bulb.

    Compare this effect to other wave and polarization demonstrations in sections G3 and M7.
    FS1

  • K8-43: RADIOWAVES - FREQ MEASUREMENT WITH OSCILLOSCOPE

    K8-43
    Experimentally determine the frequency of the radiowave transmitter.
    The signal from a radio frequency transmitter (mounted on a small stand) is picked up by the receiving antenna conencted to anoscilloscope. From the measured period of the radiowaves on the scope the frequency can be calculated. In the above photo, the period of the radiowaves is slightly greater than 12 nanoseconds, so the frequency is about 80 MHz. The transmitter should be located about 2 meters away from the receiving antenna to reduce the signal level to a readable amplitude for the scope.

  • K8-44: RADIOWAVES - COUPLING OF WAVES

    K8-44
    Illustrate inductive coupling using radio waves.
    A low-power 85MHz transmitter is coupled by an induction loop to a vertical transmitting antenna. A handheld dipole antenna with a lightbulb at the center serves as a receiver. Hold the receiving antenna near and parallel to the transmitting antenna. Change the coupling between the oscillator loop and the antenna loop by rotating the antenna loop. Coupling between the transmitter and the transmitting antenna is greatest when the light bulb between the two halves of the dipole receiving antenna glows brightly. When the loops are perpendicular there is little coupling and the bulb dims. When the loops are close and parallel the coupling is greater and the antenna bulb glows brightly.

  • K8-45 RADIO WAVES FROM SPARK

    K8-45
    Demonstrates that a spark contains radio waves
    Turn the radio on to a frequency where there is no station. Hold the battery near the radio and short it out by quickly contacting and releasing the contact using a banana wire cable. A clicking sound will readily be heard on the radio.

    Compare J3-23: Faraday Cage - Radio Waves, which can use the same radio to illustrate a related phenomenon.
    K8

  • L3-16 FOCUSING OF HEAT WAVES BY MIRRORS

    L3-16
    Demonstrates that concave mirrors can focus heat waves
    Two parabolic concave mirrors are used to focus heat from a nichrome heater and light a match.
    L3, PW1

  • L4-02 REFRACTION - BEER MUG IN WATER

    L4-02
    Illustrates refraction
    Due to refraction of the light at the walls of the mug, the mug looks like it has very thin walls and is really filled with liquid. When the mug is placed into water, as in the photograph, the real situation becomes apparent: the mug has very thick glass walls, and holds much less liquid than you think

  • L4-06 REFRACTION IN CLOUDY WATER

    L4-06
    Demonstrates a light ray bends when it enters a different medium at an oblique angle.
    The ray from the laser refracts when entering the surface of the cloudy water. The path of the laser beam in the water may be rendered more visible by adding a touch of powdered creamer to the water.

  • M7-31 TYNDALL'S EXPERIMENT - COLLOIDAL SUNSET

    M7-31
    Colloidal sunset demonstration
    The collimated white light from the bright point source passes through the empty tank and hits a nearby screen. Chemicals previously prepared are then mixed in the tank: 2.5 ml sodium thiosulfate solution in 100 ml water, and 2.5 ml concentrated HCl 1:4 dilution in 650 ml water. When the chemicals mix they begin to form a suspension of sulfur particles which act as scattering centers for the light, especially blue light at first. This leaves the light on the screen with a yellowish tint. As time passes the sulfur particles grow larger and scatter more light and light of a longer wavelength, changing the light on the screen to a bright red. Ultimately most light is scattered, leaving no light on the screen.
    M7, LS1, OM1

  • M8-01 POLAROIDS AND KARO SYRUP

    M8-01
    Demonstration of an optical cavity
    Place a glass bottle of Karo syrup between two crossed polaroids lighted from behind, then rotate one of the polaroids. The second polarizing sheet removes a small band around one wavelength of light, to produce negative colors.
    M8, M7, LS1

  • N1-05 SPECTRA - VISIBLE AND INVISIBLE

    N1-05
    Demonstrates continuous spectrum
    The carbon arc lamp is used to provide a continuous white light spectrum. Light from the arc lamp is focused by a condenser lens with iris and a 20 cm focal length cylindrical lens onto a slit. A 20 cm focal length convex lens then images the slit onto the screen through an equilateral prism. A fluorescent screen (with fluorescein) is used to show that there is ultraviolet radiation, including a strong UV line, in the carbon arc spectrum. A thermopile is used to sense infrared radiation, where the heat measured by the thermopile causes an audio oscillator to rise in pitch, so a hotter source produces a higher tone. (see I2-06 for more on this apparatus) Aiming the thermopile from the spectrum back toward the prism, it is observed that the hottest part of the spectrum is just off the red color, in the infrared.
    N1, OM1, LS1

  • N1-41: RAINDROP RAY MODEL

    N1-41
    Illustrate formation of a rainbow.
    This is a large roughly scaled model showing the refraction of light rays in a raindrop leading to the formation of a rainbow.

    ge

  • N1-43: RAINBOW - GLASS BEAD MODEL

    N1-43
    Observe an almost complete circular rainbow formed by glass beads.
    Glass beads are glued to a black screen to simulate water drops. When the screen is viewed from close up, with the light source (or sun) coming from behind the observer, the primary rainbow can be seen at an angle of about 22 degrees. The secondary rainbow is at an angle of about 88.5 degrees, and must be viewed by looking nearly parallel to the surface of the card, so it cannot be seen while viewing the first order rainbow. This is best observed on an individual basis. The dark region in the center of the photograph is a shadow of the camera taking the photograph, where the observer would position his or her head.

    Several features of this rainbow are similar to features of real rainbows: the colors are in the correct order (red outside and blue inside, a bit washed out in the central region in the photo) and are reasonably realistic, the area outside the rainbow is very dark, compared to the area inside the rainbow, and several supernumerary bows (white circles) can easily be seen inside the rainbow.

    The real primary rainbow is at about 41 degrees, and the secondary rainbow is at about 52 degrees. The higher index of refraction of the glass beads shifts the primary rainbow to 22 degrees and the secondary rainbow to 88.5 degrees.

    n1-43FireRainbow

     

  • N2-02: DIFFRACTION SPECTRA - THREE SOURCES - EXPENDABLE GRATINGS

    N2-02
    Demonstrate diffraction spectrum of white light along with line spectra of mercury and cadmium.

    Three sources are permanently mounted on a roll-around cart, from top to bottom: (1)a clear glass long-filament incandescent light bulb which produces a continuous white light spectrum, (2) a mercury lamp which produces a line spectrum, and (3) a cadmium lamp which produces a line spectrum

    These spectra are seen using 1"x2" sections of a large roll of replica diffraction grating material with 13,200 lines per inch. The pieces of grating material are relatively cheap, and may be given to the students. Tell your students to go away and look at the spectra of various lights.

    The three lamps are mounted in a vertical line so the colors of the lines are the same as those in the adjacent white light spectrum. Point out that the spectra of mercury and cadmium are very different, and generalize that observation to suggest uniqueness of the spectra for each material.

    N2, OS3

  • P4-01: Radiation Monitor (Geiger Counter)

    P4-01
    Demonstrates radioactivity, the Radiation Monitor (Geiger Counter), and some differences between alpha, beta, and gamma radiation

    Radioactive mineral sources can be examined.

    Alpha particles have a range in air of about 2 or 3 cm; you must place the source close to the Radiation Monitor to observe the alphas. Inserting a piece of paper in the alpha beam stops them! Beta particles have a longer range in air, and are mostly unaffected by passing through a piece of paper. A thin lead sheet stops the betas, but some counting may remain due to the presence of a some gammas in the beta source. Gammas are unaffected by the paper or the thin lead sheet, but can be stopped by a lead brick
    SU19

  • P4-04: COSMIC RAYS

    P4-04
    Demonstrate the existence of cosmic rays.
    Two scintillator paddles with phototubes are used to detect cosmic ray muons. A coincidence unit is used to obtain cosmic ray coincidences between the two paddles when they are positioned along a vertical line. Set one detector on a chair and hold the second detector above it to see coincidences; move the upper paddle horizontally to demonstrate that the muons are coming straight down from the upper atmosphere. The bottom paddle can be placed on a chair, a student lies on that detector, and the second detector is held over the student to demonstrate that cosmic rays are passing through the student (or other victim). Read more about the new design at https://www.i2u2.org/elab/cosmic/teacher/detector.jsp
    FS1

    p4-04p4 04newcrop

     

  • P4-32: CLOUD CHAMBER - TV

    P4-32
    Allow class observation of alpha and beta particle paths with a cloud chamber using TV.

    Sealed sources of alpha particles and beta particles are used with a small student cloud chamber to observe the paths of alphas and betas. The alpha paths are very distinct and clear, whereas the beta paths are more diffuse. Cosmic ray products or gamma rays are also visible, but less distinct. A TV camera views the "action," which is displayed on a monitor or on the rear projection system in the lecture halls (photograph at right).

    The cloud chamber uses dry ice for cooling, and uses alcohol to remove heat from the chamber and to provide the atmosphere of supersaturated alcohol vapor which condenses along the path of the ionizing particles to make the path visible.
    Nuclear Physics

    p4-32a