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  • L3-33: VANITY MIRROR

    L3-33
    Show the image produced by a cocave mirror.
    A standard hand-held vanity or shaving mirror, flat on one side, concave on the other. Pass it around for the class to examine, or simply use it to admire yourself.

  • L5-03: FISH IN TANK - TOTAL INTERNAL REFLECTION

    L5-03
    Illustrate total internal reflection.
    The fish is seen once directly through the side. Other views are reflected off the back of the tank, reflected off the water surface, and reflected off both the water surface and the back of the tank. To see this view the tank must be observed from below and at an angle, as shown in the photograph at the right.

  • L6-07: MICROWAVES - LENS

    L6-07
    Demonstrate that a paraffin lens can focus microwaves.
    When the 12cm microwave transmitter and receiver are placed about 50 cm apart the receiver picks up the microwaves and displays them on an overhead projector meter. Positioning the lens at an appropriate point between the transmitter and the receiver focuses microwaves onto the receiver, increasing the meter reading. The geometry can be optimized by moving the receiver along the optic axis.

  • L6-08: REAL IMAGE OF CONVERGING LENS - LIGHT BULB

    L6-08
    Show the real image of a converging lens.
    An incandescent bulb with printing on the top is used as an object to be imaged with lenses of different focal lengths. Hold the lens above the light bulb at a distance slightly greater than the focal length of the lens to cast an image of the trademark onto the ceiling. Change lenses to change the magnification. (10cm and 20cm focal length lenses tend to work best in most rooms, but 5cm, 30cm, and possibly others can also be available upon request.)
    OM1, LS1

  • L6-14: IMAGE OF CONVEX LENS - WITH AND WITHOUT BAFFLE

    L6-14
    Encourage thought regarding how an image is formed.
    An arrow/circle cross object is imaged on a screen by a 150mm focal length convex lens, as seen in the center photograph above. The experimental setup is shown below, with the object at the left, the lens in the center, and the image screen at the right in the photograph. A paper baffle is then stuck onto the lens, as seen in the photographs below, blocking half of the light passing through the lens. What happens to the image? Encourage your students to make a prediction. Will it remain unchanged; will it become brighter; will it become fainter; will the left side be gone, or will the right side be gone? Shown also are the image without the baffle on the focusing lens and with the baffle on the focusing lens. The image with the baffle in place is clearly fainter than the original image, as can be seen.
    OM1, OM2, LS2, office

    l6-14a

    l6-14b

    l6-14c

  • L6-35: CHROMATIC ABERRATION - POINT SOURCE AND 20 CM LENS

    L6-35
    Show the effect of chromatic aberration in a lens.

    Two 20cm convex lenses are available: a simple spherical lens and an achromat. Light from the point source is focused onto a slit by a cylindrical lens placed immediately in front of the source, which in turn is imaged by the 20-cm spherical lens onto a distant screen, as shown in the photograph at the left above. The screen is then rotated as shown at the right above to increase the dispersion at the image.

    The image of the achromat, shown at the right below has virtually no chromatic aberration compared with that of the ordinary simple lens, seen at the left.

    l6-35a

    l6-35b

    l6-35c

  • L6-42: DISTORTION AND CORRECTION

    L6-42
    Illustrate pincushion and barrel distortion and correction thereof.
    This is a two-lens system with an iris between, modeling camera or projector lenses. For the purpose of this demonstration there are apertures preceding and following the lens doublet. Closing only the preceding aperture results in barrel distortion, and closing only the following aperture produces pincushion distortion. Closing only the aperture between the two lenses results in no distortion.

  • L7-05: VIDEO CAMERA WITH VARIOUS LENSES

    L7-05
    Demonstrate various lenses for a video camera.
    Interchange a standard 45mm lens and a zoom lens on the TV camera to show on the monitor what the optics does. Install one of the five close-up lenses onto the standard lens to view small objects. The above right photograph shows the zoom lens controls. The photographs below show the near point for the standard 45mm lens without and with a supplemental 10cm close-up lens.

    l7-05a'

    l7-05b

    l7-05c

  • L7-06: MINICAM WITH WIDE-ANGLE, TELEPHOTO AND MACROZOOM LENS

    L7-06
    Illustrate the optics of a "modern" minicam.

    Illustrate how the various optical features of the camera work as well as other features of the minicam as desired. Show the picture on the video rear projection screen above the blackboards. Controls for the camera are shown in detail in the photographs below.

    The photograph at the center shows the main focus and shutter controls. At the right are the manual controls for focus and zoom, along with the macrozoom control lever (near bottom of picture). The photograph at the left shows the ON/OFF button for videorecording, the built-in microphone (top), and the rocker switch for telephoto and wide angle adjustment (center of picture).

    l7-06a

    l7-06c

  • L7-15: MICROSCOPE

    L7-15
    Demonstrate how the optics of a microscope produces a magnified image.
    A mirror mounted under the microscope stand is placed to light up the subject. Light bounces off the mirror, passes through and around the subject (mounted firmly to a microscope slide), and into the objective lenses. The objective lens of a microscope is small and spherical, with a short focal length. It brings the image of the object into focus at a short distance within the microscope's tube. The image is then magnified by a second lens, called an ocular lens or eyepiece.

    l7-15-microscope-diagram

  • L7-43: Telephoto Lens Model - Point Source

    L7-43
    A model of a telephoto lens
    The demonstration serves as a model of the assembly and function of a telephoto lens attachment. A point source with a small crossarm baffle serves as an object imaged by a sequence of lenses – a 150mm focal length converging lens, a -100mm focal length diverging lens, and a 300mm focal length converging lens, to focus on a distant screen. Other lens combinations can be available upon request.

  • M7-05: ROPE AND COOKIE COOLERS

    M7-05
    Demonstrate the concept of polarization of a transverse wave.

    A rope is held at the two ends so that vertical and horizontal polarized waves can be sent from one end to the other. The rope is then inserted between the two cookie coolers. When the two cookie coolers are aligned, they can pass a rope wave polarized in that direction but when they are crossed no wave can pass.

    This can be used as an analogy to light waves, which are also transverse waves. Technically the mechanism of polarization in electromagnetic waves is somewhat different and more complex than this model. In an advanced class, this can be used in conjunction with Demonstration M7-01: MICROWAVES - POLARIZATION.
    M7

    m7-05a

     

  • M7-17: REFLECTION OF LIGHT FROM DIELECTRIC AND CONDUCTOR

    M7-17
    Demonstrate how light is polarized when it reflects from dielectric surfaces, and remains unpolarized after reflecting from conducting surfaces.

    When sunlight reflects off a horizontal dielectric surface such as water in a lake, wet roads, or even dry smooth roads, the reflected light is largely horizontally polarized. Polaroid sunglasses are oriented vertically so they remove "glare," which is horizontally polarized specular reflection from such surfaces.

    Position the point source so that it reflects from the lecture table onto the front white screen at about the Brewster angle. Rotating a polaroid in the light from the point source before reflection shows clearly that the reflected light is polarized. Individually viewing the reflected light directly using a polarizing filter demonstrates the value of polaroid sunglasses in removing glare. Placing a piece of aluminum foil where the light hits the table demonstrates that reflection from a conducting surface is not polarized.

    The photographs above show the polarization axis (a) parallel and (b) perpendicular to a dielectric surface, and (c) parallel and (d) perpendicular to a conducting surface (a sheet of aluminum foil).

    m7-17am7-17bm7-17cm7-17d

     

  • M9-03: CIRCULAR POLARIZATION - STICK MODEL

    m9-03
    Model of circularly polarized electromagnetic wave.
    Sticks emanating from a central rod create a model of a circularly polarized electromagnetic wave, as the wave is moved through space at the speed of light by the instructor.
    FS1

  • N1-01: PRISMATIC SPECTRUM OF WHITE LIGHT - POINT SOURCE

    N1-01
    Demonstrate continuous spectrum
    This is a convenient setup for showing the visible spectrum. A bright point source is used to provide a continuous white light spectrum. Light from the point source is focused first by an integral condenser lens and iris and then a 20cm focal length convex cylindrical lens onto an adjustable slit. A 20cm focal length convex spherical lens then images the slit through an equilateral flint glass prism onto a screen. For mechanical drawings of the original point source, see lecdem.physics.umd.edu/images/Demos/point%20source%20plans.pdf
    FS1, LS1, OM1

    n1-01a

  • N1-31: SUN DOG - MODEL

    N1-31
    Show how a "sun dog" is formed.
    A prism is mounted below a fast rotator, approximating the effect of hexagonal ice crystals. Rotation of the crystal has the same effect as scattering off many flat hexagonal ice crystals aligned along the horizontal plane but rotated randomly in that plane (See demonstration N1-32 ICE CRYSTALS - PAPER MODELS). The "sun dog" consists of a relatively sharp cutoff at 22 degrees, the minimum angle of dispersion for ice crystals, with a long tail of decreasing intensity. For the prism the deflection angle is greater than 22 degrees because the index of refraction of glass is greater than that of ice. The outer thirds of each face of the equilateral prism is covered by tape, making it appear to the incoming light more like a hexagonal ice crystal.

     

    n1-31an1-31b

  • N2-09: SPECTROPHOTOMETER

    N2-09
    Show how a spectrophotometer works.
    A bright point source of light with condenser lens and iris is incident on a slit. The slit is imaged by a 20 cm focal length convex lens onto a plane near the end of the rotating extension arm attached to the main optical rail. A spectrum is obtained by inserting a prism at the center of rotation of the rotating arm. A radiometer is attached to the rotating arm so that it rotates through the spectrum, displaying the intensity of the light.

  • N3-31: COLOR SEPARATION TRANSPARENCIES

    N3-31
    Illustrate color mixing of negative color transparencies.
    Four negative color transparencies of the subject girl with umbrella are shown: one taken in yellow light, one taken in cyan light, one taken in magenta light, and one taken in white light (left picture, upper left image). When the three individual subtractive color transparencies are superimposed (right picture, right image) the result is the same as the white light transparency (right picture, left image).

    This demonstration illustrates how real color films work.
    N3

    n3-31a

  • N3-33: MAXWELL'S EXPERIMENT - THREE-COLOR MIXING

    N3-33
    Demonstrate three-color mixing with positive colors.
    Three identical slides taken in white light are projected superimposed on the same place by three slide projectors, but each is filtered by one of the three primary color filters: red, green, and blue. Add the three together to get the same effect as the original slide, which can be displayed with white light on a fourth slide projector for comparison.

  • N3-41: SPLITTING OF SPECTRUM INTO COMPLEMENTARY COLORS

    N3-41
    Show complementary colors by removing a band from the white light spectrum.
    A baffle is inserted into the focal point of the white light spectrum, removing a narrow band of color. The light removed is reflected by the baffle to a mirror which reflects it to the screen, adjacent to the rest of the spectrum, which has been recombined and focused onto the same screen. The two parts of the spectrum are complementary colors.

    The baffle can be moved across the spectrum to obtain various complementary color combinations.