Louisiana State University at Eunice-Division of Sciences
P.O. Box 1129 Eunice, LA 70535
Phone: (318) 550-1247 or (318) 457-7311 Ext. 247
E-mail : sshabani@lsue.edu

Abstract

Approximately about the size of a laboratory He-Ne laser device (11"x 5"x3.5"), the LCM is an electro-mechnico-optical device which primarily decomposes white light (color) into its constituent colors; colors of the rainbow and also recombines these seven constituent colors to produce white color. The LCM's secondary function is to show that two primary colors (i.e. blue and green) will produce a secondary color (cyan).

Approximate size:   11" x 5" x 3.5"

Requires electrical power? No. LCM is battery operated.

Is this apparatus intended for use with and overhead projector? No

Will you be present to set up your apparatus? Yes

Equipment required to construct apparatus:

Heavy cardboard box (housing) one 6 volt battery one DC motor, variable or fixed speed (type 128-7, or 1.5-3volt, 10,000 rpm) one high intensity Mini Maglite flashlight is used to produce a stream of light. connecting wires with test clips one potentiometer ( 20 ohms, 2 watts, optional) hard foam is used as a stand for motor several colored disks a cylindrical dispersion module to act as a prism ( from a BIC or PILOT pen external cover) A 3" long threaded shaft with connective gear to the DC motor and screw connection to the color disks.

Item Source/Store Part Number Cost

6 volt battery Wal-Mart $7.00
DC motor Radio Shack $6.50 OR DC motor Radio Shack 273-223 $2.50
high intensity Maglite flashlight Wal-Mart $11.50
connecting wires & clips Radio Shack 270-374 c $ 3.00
potentiometer Radio Shack 271-265 A $ 3.50
coloring pen & white card board for disks Wal-Mart $ 4.10

Total cost...................................................................................................................$ 35.60

Sketch

Description

Light and Color Machine consists of three general sections:

1. Housing This compartment has the approximate size of 11" x 5" x 3.5". This box houses battery, motor and its attachments, flashlight and the light dispersion module. The potentiometer could be installed on the box.

A complete diagram of the LCM with the proper labels and the pictures will be mailed.

2. Electromechanical color mixing section a) color disk(s) made of thick paper or plastic which consist of different color compositions (i.e. Red, Orange, Yellow, Green, Blue, Indigo, Violet for white light) are being used for mechanical mixing. Diameter of these disks depends on the RPM of the motor.

b) A DC motor with a variable or fix speed is used to rotate the disks. The motor is attached to a small threaded shaft of 3" long with the disks mounted at the top of the shaft. The connecting wires from the motor are either directly or through a potentiometer in contact with the battery.

c) The 3" shaft is threaded on its upper portion to have disks secured on it with the use of a screw bolt and a metallic gasket. At the bottom, this shaft is connected to the motor through a cylindrical metallic connector and ready to be spun.

d) Through the use of a potentiometer/rheostat or directly, a 6 volt battery is connected to the DC motor. A potentiometer/rheostat is used to produce a variable speed so that the observer sees the process slowly from its inception. This could eliminate, for the less experienced obsever, the perception that the mixing phenomena is a hoax.

3. Optical part- Light decomposition a) This part of the LCM consists of a high intensity flashlight with a variable focus beam which can send a stream of light to the dispersion module. This flashlight is inserted through an opening at the top of the housing box and it is free to move in all three direction.

b) A 4.5" long dispersion module which is a hollow 6-sided external part of an ordinary pen is attached horizontally to the open end of the housing box. This module is made of a transparent hard plastic which will act as a prism and is mounted between two walls of the box at the height of 1" from the bottom of the box.

A certain angle (about 40 degrees) must be maintained between the incident light beam and the dispersion module for the decomposition of white light to take place. This may take a few minutes to be achieved, therefore, indicating to the students the angle dependency of the dispersion phenomena when they try it out.

This colors of rainbow then could be projected on the classroom wall (a dark corner) or on a white sheet of paper.