Inquiry 8: How Does It Work? Binoculars, Periscopes, and Kaleidoscopes
Binoculars are really just two refracting telescopes joined together with a hinge. Soon after telescopes were invented, people started to fasten two of the long tubes together to make binoculars. These long binoculars, however, were heavy and difficult to handle. Since it was difficult to keep these tubes parallel to one another, the image seen was often doubled.
Around 1900 a German physicist named Ernst Abbe made a pair of binoculars using prisms that reflected the incoming light twice. This meant that it was possible to make a shorter instrument. Also, by using two prisms the image that formed appeared right side up.
Binoculars are currently found in three designs: 6x30, 7x50, and 8x30. The first number refers to the magnification of the binoculars and the second number gives the diameter of the objective lens in millimeters. When using binoculars, you look at an object and light reflects off the object and enters the front of the binoculars through the objective lens. This forms an image that is upside down and reversed. Prisms correct the image before we see it through the magnifying eyepiece lenses.
Life Science - Encourage students to use binoculars to observe birds. They can record some of the following features used for the identification of birds: the shape and color of the eyes, feet, color of the plumage, shape of the head, shape of the tail feathers, and beak shape and color. They should record in their science notebooks some of these features, sketch what they observe, or both. Then, using guidebooks for the identification of birds, they could try to determine what kind of birds they observed.
Periscopes are instruments that allow the viewing of objects that are not in the direct line of vision. They are often found in submarines and may have tubes up to 10 meters long. Tanks also contain periscopes that allow people inside of a tank to view the surrounding area while remaining protected inside of the vehicle. The development of fiber optics led to the development of other types of periscopes that allow doctors to view inside the human body without having to perform major surgery. These types of periscopes are called endoscopes or cystoscopes and are very useful in the medical field.
Make a Periscope - Have students construct a periscope by using the directions that follow. The activity will encourage them to experiment with mirrors and the correct placement of them in the scope.
*Transparency film on black construction paper works like a mirror and the materials are accessible and inexpensive.
What will the students do?
Students should cut the tops off of two milk cartons and then cut a hole about 5 cm in diameter in one side of each carton near the bottom. They will tape a mirror, tilted at a 45-degree angle, in the bottom of each carton, with the shiny side facing the hole. Then, students should tape the two cartons together so that the holes are on opposite sides of the periscope. In other words, where they look into their periscopes should be on the opposite side of the tube from the hole where light is coming in. Students should then answer the questions that appear on the student page in their science notebooks.
The kaleidoscope was invented by Sir David Brewster around 1816 and patented the following year. The device uses the image-forming properties of combined inclined mirrors. Depending on the number of mirrors and the angle between them, the kaleidoscope will produce multiple symmetrical patterns. Since its introduction, the kaleidoscope has been sold primarily as a toy, but has practical uses as well.
A simple kaleidoscope is made of two thin, wedge-shaped mirror strips touching along a common edge or a single sheet of bright aluminum bent to an angle of 45 or 60 degrees. The mirrors are enclosed in a tube with a viewing eyehole at one end. At the other end is a thin, flat box that can be rotated. The flat box is made from two glass disks, the outer one ground to act as a diffusing screen. In the box are pieces of colored glass or beads. When the box is turned or tapped, the objects inside tumble into different groups and when the diffusing screen is illuminated by natural or artificial light, six or eight different symmetrical images appear. The number of combinations and patterns is without limit.
There are five different types of kaleidoscopes. The chamber kaleidoscope has an enclosed object case with free-tumbling jewels, glass, beads or other objects. The liquid chamberscope has an object case filled with liquid (usually glycerin) in which the jewels, glass beads, or other objects float. The wheel scope has one or more wheels at its objective end that may contain glass, translucent rocks like agates, pressed flowers, beads, jewels, or other objects. The refillable scope features a removable object chamber. The contents of the chamber can be changed and users can experiment with their own assortment of colors and objects. The teleidoscope uses mirrors and lenses alone so that anything that is viewed, is multiplied.
Make a Pringles Can Kaleidoscope - After discussing kaleidoscopes with your students, have them construct their own. They should be allowed to choose to construct either of the kaleidoscopes described below, based upon whatever materials are most readily available to them.
What will the students do?
Students will make a hole in the center of the metal bottom of the Pringles can with the hammer and nail. With the point of the scissors or other object, they should expand the hole to a 1.5 cm diameter. This will be the eyehole of the kaleidoscope so it is important that there are no sharp edges. Next, students will cut out a 4 cm square of transparency film. They should glue the transparency square over the eyehole of the kaleidoscope.
From the file folder, students will cut three 7.5 cm x 19.5 cm strips. They should also do the same with the black construction paper and the transparency film. Then, students should glue the strips together in the following order: file folder, black construction paper, and then transparency film. If done properly, they should each have 3 sets of layered strips. The transparency on top of the black paper should provide a mirror-like surface.
Students will place each set of strips into the open end of the can, edge to edge, with the mirror surfaces facing the center of the can. Looking into the can, the top edges of the strips should form an equilateral triangle. They should then cut 2 more strips from the file folder, this time 23 cm x 1.5 cm. Subsequently, students will fold one strip in half the long way and glue the folded strip along the long edge of the unfolded strip.
Next, students will glue the combined strips around and along the inside edge of the open end of the can above the mirrors and let the glue dry. The folded strip should be closest to the mirrors. In the meantime, they should cut a circle of transparency film with a diameter of 7.5 cm (the same diameter as the opening of the can) and place it inside the open end of the can with its edge against ledge created by the folded strip. The circle should be glued in place with rubber cement.
After all glue has dried and the students have placed various objects such as beads, shells, or gemstones, on top of the transparency circle, their kaleidoscopes are almost complete. Once they have placed the lids back on the cans they can begin using the devices.
Make a Paper Towel Roll Kaleidoscope - Have students design their own kaleidoscopes out of paper towel rolls.
What will the students do?
In this version of the kaleidoscope activity, students will trace the top of the paper towel roll on the file folder. Then, using a compass, they will draw a circle 1.5 cm larger around the circle they traced and cut out the larger circle. They should then make a hole about 1.5 cm in diameter in the center of the circle, which will be the eyehole for the kaleidoscope.
Students will make small cuts around the outer edge of circle from the edge to the traced line. The cuts should be made about every 1.5 cm around the circle and will form little tabs. Next students should cut out a piece of transparency film large enough to cover the eyehole and glue it over the eyehole. The circle should then be placed on the end of the roll with the transparency piece facing inside the roll. Students should fold down the tabs all around the outside of the roll and secure it to the roll with masking tape.
Students will then cut from the file folder three 6.5 cm x 27 cm strips and do the same with the black construction paper and the transparency film. The strips should be glued together in the following order: file folder, black construction paper, and then transparency. Each student should have 3 sets of layered strips and the transparency film on top of the black paper will provide a mirror-like surface.
Next, students will place the strips side-by-side, mirrored surface down, on top of their work surface. They should then put masking tape across the strips at the top and bottom and fold the connected strips to form a three sided column 27 cm long with the mirrored surface facing inside. They should tape around the column to hold it together. Looking into the column, the top edges of the strips should form an equilateral triangle. Students should place the column into the open end of the tube.
From the transparency film, students should cut out two circles using the directions in steps 1 and 4. They will then have two circles of transparency film with 1.5 cm tabs around them. They should fold back the tabs of one of the transparency circles then place it into the open end of the tube so the circle is touching the mirrored column and the tabs are facing out. Students should secure the circle to the tube with tape and place their choice of colorful objects into the open end of the tube. Finally, they should place the other transparency circle over the open end of the tube, folding down the tabs all around the outside of the roll and securing it with masking tape.
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