Grinnell College Physics Museum

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Jolly Balance

A Jolly balance has a weak spring so that it stretches a great distance when a small force is applied. If a small, known force was applied to the pan and the resulting extension of the spring noted, the spring constant could be calculated and the balance then used to measure other small forces. The name comes not from the attitude of its users but from the name of its 19th century inventor

Nicol Prisms

A Nicol Prism is a device to produce polarized light. It is made from a crystal of calcite, which is cut along a precisely determined plane and then cemented back together with Canada balsam. When a beam of light enters the crystal along the line defined by the mounting of the crystal, it is broken into two beams. In the two beams the planes of vibration of the electric field vector are perpendicular to one another. When the two beams strike the cemented cut, one is passed through and the other is deflected to the side and absorbed in the mounting.

Laser

This is the first laser owned and used by the Grinnell College Physics Department. It is a helium-neon laser, and the gas inside the tube was excited by a radio-frequency field produced by an oscillator. This laser was purchased by Bob Noyce, who experimented with it for a short time and then brought it, carried on his lap on the airplane, to Grinnell and presented it to the Physics Department. The orange plastic cover is lying behind the instrument.

Lens on Stand

This lens on a ball mount has been used for many years for lecture demonstrations. Although neither date of purchase nor maker is known, it certainly has been part of the college's equipment since the early 1900s if not earlier.

Sonometer

The sonometer is an apparatus by which the transverse vibrations of strings can be studied. It is also called the monocord because it often has only one string. On the box are two fixed bridges, near the ends, and at one end is a pulley. A string, often a steel wire, is fastened at one end, run over the bridges and the pulley, and attached to a weight holder hanging below the pulley. Weights can be added to the holder to produce tension in the wire, and a third, movable bridge, can be placed under it to change the length of the vibrating section of the string. This instrument was purchased from Queen & Co. The date is not known with certainty, but it probably was 1905 or earlier.

Helmholtz Resonators

Before the advent of electronic spectrum analyzers, Helmholtz Resonators were used to detect different frequencies in a sound wave. This set of nineteen resonators was purchased for $70.

Savart Bell and Resonator

The hemispherical bell is made to vibrate by stroking it with a violin bow. If the resonating cylinder is turned toward the bell and its length adjusted by the slide until its resonate frequency matches that of the bell, the sound is intensified. The cylinder can be moved away from the bell and tilted up and down. This piece of equipment cost $20 when it was purchased from Queen & Co. of Philadelphia.

Almy's X-Ray Photograph of Keys and Coins

A photographs taken by Professor Almy in February 1896. The colors are the result of fading. Originally all would have been black and white.

Almy's X-Ray Photograph of Frog

A photograph taken by Professor Almy in February 1896. The colors are the result of fading. Originally all would have been black and white.

Almy's X-Ray Photograph of Hand

A photograph taken by Professor Almy in February 1896. The colors are the result of fading. Originally all would have been black and white.

Ulysse Nadin Chronometer

This chronometer is five inches in diameter. It is mounted in a box with a glass lid (below the wooden lid) and is in gimbals for use on a ship. The lettering on the face reads Ulysse Nardin Locle Suisse A tag with the chronometer says that it was checked by the US Naval Observatory on September 28, 1945.

Solar Microscope

A solar microscope was placed in a hole in a window shutter with the mirror outside and the barrel extending into a room. Sunlight was reflected by the mirror through condensing lenses, a slide carrying an object to be observed, and projection lenses. The image was projected on a screen in the room. This microscope has no maker's name on it, and its date is unknown. The solar microscope was invented in 1740 and remained popular into the next century. This instrument probably is older than Grinnell College, possibly dating to the late 18th century and certainly no later than the early 19th century.

Early Phonograph

This "talking machine" is on loan to the museum by the family of Professor Ben Graham. They used it in Massachusetts in the late 1890's. The recording is on a wax cylinder instead of a flat disk. The horn is not original; the original horn was much larger.

Chronometer

This small chronometer, about three inches in diameter, was made by Northwest Instrument Company of Seattle, Washington. The date of manufacture is unknown. It is mounted in gimbals for use on a ship.

Homemade Galvanometer

When Frank Almy came to Grinnell College in 1893 to teach physics, laboratory equipment was not as readily available as it was later. Probably the cost of equipment also placed a severe constraint on purchases. Almy made a number of galvanometers, some of which survive. One of those galvanometers is shown here. It had a mirror attached to small magnets suspended between coils.

Epinius' Condenser

This is a capacitor with adjustable plates and a plate of glass which can be inserted between the plates. With static charges on the plates, the effects of plate separation and nature of the dielectric between the plates can be studied. This was purchased from Queen & Company, but the date is unknown.

Spectrometer

Manufactured by Societe Genevoise Purchased from James W. Queen & Co.

Homemade Geiger counter

Grinnell's first Geiger counter which unfortunately is broken.