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PiP Oct 2015

  • L1-22: OPTICAL BOARD - PINHOLE CAMERA

    L1-22
    Demonstrate how a pinhole "image" is formed.
    The camera is represented by the region between the two baffles on the optical board. The left baffle has a small slit representing the pinhole, and the right baffle has a light surface to make the ray visible. Hold the carousel projector by hand and shine it at the "camera." from a position at the left of the optical board. The position of the source and the position of the "image" are related.

  • L2-01 OPTICAL BOARD - PLANE MIRROR

    L2-01
    Demonstrates reflection from a plane mirror

    This demonstration shows that the angle of incidence is equal to the angle of reflection. A bright white light source is directed through a baffle with several slits, producing a set of rays. Lenses are used to collimate these rays, and they are then reflected off of a long plane mirror. If the lenses are adjusted such that the incoming rays are approximately parallel, the reflected rays will be as well.
    Engagement Suggestion
    Optionally, you can use slits with colorful filters to show that this is good for all colors. Challenge students to predict what will happen if you switch to the color filters – will different colors reflect at different angles? Why or why not?
    Background
    Unlike light diffracted through a lens or prism, reflected light from a surface is unaffected by the frequency of the light. The reflection off of a flat mirror is dependent only on the angle the light strikes at. Thus, there should be no chromatic aberration in a reflecting telescope, one reason they are valuable for astronomical use.
    FS1

  • L2-06 MAGIC TRICK - DISAPPEARING RABBIT

    L2-06
    Plane-mirror magic trick


    A box has been divided diagonally by a flat mirror. A hatch in the top lets a toy rabbit be dropped in to the space behind the mirror.
    Engagement Suggestion
    • • The box is first shown to the group. Then the black cloth is placed over the front of the box, the trap door on top of the box opened, and the rabbit put into the box through the trap door.
    • • Invite students to predict what they will see when the cloth is removed.
    • • When the black cloth is removed the rabbit has vanished into thin air (behind the mirror).
    • • Challenge then to analyze how this has happened
    • • Explain the positioning of the mirror, and invite them to consider what it would look like with the mirror at different angles.
    Background
    Because the mirror is mounted at a 45 degree angle, it reflects the bottom of the box to look like the rear of the box. So viewed from the front, the box appears empty. This is a common technique for creating such illusions.
    L2

  • L2-22: INFINITY MIRROR

    L2-22
    Illusion with half-silvered mirror.

    A single square array of small lights has a full-silvered mirror in back and a half-silvered mirror in front. A long black box placed in back of the infinity mirror appears to have many rows of lights in it until it is removed!

    An interesting sidelight is to use this device to indicate the dynamic range of the eye. Each successive row of lights has an intensity of about 1/2. Approximately twenty rows of lights can be seen by the typical naked eye, so the dynamic range of the eye is at least as great as 2^20, or 1,048,576 to 1.
    L2, FS1

    l2-22a

  • L3-11: OPTICAL BOARD - CONCAVE SPHERICAL MIRROR

    L3-11
    Illustrate reflection from a concave spherical mirror.
    A series of parallel rays are formed using a slit baffle and with concave and convex lenses. These rays are incident onto a concave spherical mirror, which focuses them to a point with some spherical aberration, as can be seen in the photograph. Number and spacing of rays are adjustable by choice of baffle and position of baffle. A baffle with sets of rays of different color can be used to draw attention to the different aberration of different sets of rays.
    FS0

    l3-11a

  • L3-18: FOCUSING OF HEAT WAVES - OVERHEAD PROJECTOR

    L3-18
    Illustrate focusing of heat in a very dramatic way.

    This demonstration uses one of the old overhead transparency projectors that focuses the light by a large parabolic mirror under the platform (rather than a Fresnel lens on the platform as in newer models), as seen in the images above. The heat filter and the mirror system above the projector have both been removed. There is sufficient heat focused about two feet above the projector to burn a piece of black paper in a few seconds. In a dark room, the focal point can be clearly seen as the smoke from the paper scatters the light.

    Engagement Suggestions

    Invite students to predict what would happen if you used white paper rather than black.

    • • Would it still burn?
    • • Would it take more or less time to ignite?
    Background

    This demonstration illustrates two important points. It clearly shows that light can be focused to a point by a curved reflector. It is also an illustration of infrared radiation, and the connection between light and heat. When appropriate to the course, consider combining this with a discussion of the wavelengths of the electromagnetic spectrum, and the relationships of energy, heat, and temperature.
    FS1

    l3-18a

  • L3-21: LIGHT BULB AND PARABOLIC MIRROR

    L3-21
    Optical illusion with real image of a concave mirror
    A light bulb is mounted upside down in the black box and positioned at the center of curvature of the mirror. The image is real, inverted, and located at the same position as the object, as seen in the photograph. The bulb can be unscrewed and removed, but it remains lit in the socket! This has a limited field of view, but can be rotated on the stand so that all viewers can see it.
    L3

  • L3-31 GIANT 160cm MIRROR - CONCAVE AND CONVEX

    L3-31
    Demonstrates images from concave and convex mirrors
    This five-foot diameter, 132cm (252-inch) radius of curvature parabolic mirror was originally designed as a solar collector on a satellite. Both convex and concave sides can be used with large classes or individually.

    Students can stand in front of the concave side at different distances to find the focal point. Invite students to predict the orientation of the image they see at different points, then try it out.
    FS0

  • L4-01 OPTICAL BOARD - RECTANGULAR SLAB

    L4-01
    Demonstrates refraction. Shows displacement of rays in a uniform slab of glass
    A slit baffle with concave and convex mirrors are used to produce a beam of parallel rays of light. A rectangular slab of lucite placed at an angle in the rays of light produces refraction at each surface, leading to displacement of the light rays. The central ray in the picture is reflected internally off the end surface of the slab and directed upward.
    FS0

  • L4-04: REFRACTION - CAN IN WATER TANK

    L4-04
    Illustrate refraction
    The can rests halfway into a water bath. Viewed at an angle, the can appears discontinuous at the water surface. The wimps who can't explain the neat picture at the left can go with the more classic view at the right.
    L4

    l4-04a

  • L5-02: TOTAL INTERNAL REFLECTION IN LONG TANK

    L5-02
    Demonstrate total internal reflection of a laser light.
    The laser light enters the end of the water tank and undergoes a series of internal reflections from the top surface of the water and the bottom of the tank.
    L5, LS1

  • L5-13: PLEXIGLASS SPIRAL WITH LASER

    L5-13
    Demonstrate total internal reflection with laser light.
    Due to total internal reflection the light from the laser remains mostly confined within the spiral plexiglass rod, and only exits at the end, where the angle between the surface and the incoming light exceeds the critical angle. Actually, some light escapes at scratches along the spiral, as can be seen in the photograph.
    L5, OM1

  • L5-14: LASER AND PLEXIGLASS TUBE

    L5-14
    Demonstrates total internal reflection
    The laser beam enters the plastic tube at a cutout along the top edge, and follows around the tube while spiralling downward

  • L5-23 FIBER OPTICS TREE

    L5-23
    Demonstrates total internal reflection
    An array of optical fibers is mounted above a light source with coloured filters. The light is guided along the fibers by total internal reflection, creating an attractive display.
    L5

    Geometrical Optics

  • L6-01: OPTICAL BOARD - CONVERGING SPHERICAL LENS

    L6-01
    Show focusing of a spherical (cylindrical) convex lens.
    Parallel rays incident on an 18 inch long convex cylindrical lens converge at the focal point of the lens. For a large aperture the spherical aberration is clearly seen, and chromatic aberration can be seen by blocking part of an extreme ray. Number of slits, and their color and spacing, can be changed by choice of slit baffle and distance of baffle from source.

  • L6-21: OPTICAL BOARD - DIVERGING SPHERICAL LENS

    L6-21
    Determine the focal point of a concave lens.
    Parallel rays incident on a diverging plano-concave spherical lens appear to emanate from the focal point of the lens. Optionally, two plano-concave diverging lenses can be placed together to increase the divergence and decrease the focal length. A slit baffle with concave and convex lenses may be used to create a set of parallel rays, which can be varied in number, color, and in spacing.

    geo

  • M1-01: LASER DIFFRACTION - FIXED SINGLE SLIT

    M1-01
    Demonstrate single slit diffraction.
    Position single slit in holder on cross-carriage in laser beam to obtain diffraction. Pattern can be shown on a distant screen, or the small screen shown in the picture. Magnification with the cylindrical lens can be used as necessary. One slide with four slits is available: 0.2mm, 0.04mm, 0.08mm, and 0.16mm, as well as individual slides of 0.12mm, 0.25mm, and 0.5mm.
    FS1

    m1-01b

     

  • M4-25: INTERFERENCE IN LARGE SOAP FILM - SODIUM AND WHITE

    M4-25
    Large interference demonstration for lecture hall use.

    Soap film interference is created in a large rectangular area, shown above for sodium light and for white light, using the apparatus photographed below. The light sources are inside the large wooden box, and reflect off the screen to yield a very uniform, broad source. The interference patterns created are very large and possess extraordinarily beautiful saturated colors.

    NOTE: The audience views this demonstration from the left in the photograph of the equipment to see the patterns in the photographs at the top above.

    m4-25bm4-25a

     

  • M6-11: HOLOGRAM - MULTIPLEX - BASEBALL

    M6-11
    Rotating 360 degree multiplex hologram.
    The hologram, lit by a clear long-filament bulb in the spherical base, shows motion of the ball players as the frame rotates. This is a neat gizmo, and really gets the attention of young children.

  • M7-03 TWO POLAROIDS AND LIGHT SOURCE

    M7-03
    Demonstrates polarization of light
    The first polaroid circle polarizes the light. Rotating the front polaroid causes the light to become alternately brighter (polaroids aligned) and dimmer (polaroids crossed). This is best performed with a semi-diffuse light source, such as an incandescent lightbox.
    M7, LS1
    Polarization