III. LASER BULLSEYE

2008 rules

A. Objective

The objective of the Laser Bullseye is to use the supplied optical elements as well as team member optical computational skills to direct a laser beam to the bullseye of an arbitrarily placed target, located behind the laser's position.

B. Apparatus

The following will be available (See the diagram):

1. A laser in a fixed position so that the direction of its beam when turned on will be known to the contestants. It will point away from the chalk board as shown.

2. A semi-circular dish filled with water will be placed 10 cm in front of the laser in the path of the beam. When rotated laterally as shown in the diagram, it will provide an angular displacement of the laser beam. (The angle of this dish will be set by the judges and will be randomly determined by the luck of the draw.) Judges will decide how to set this.

3. A mirror placed at the end of a meter stick may be moved in 3 ways:

• (1) with end of the meter stick as it pivots about its other end;
• (2) about a horizontal mirror axis to provide vertical direction changes;
• (3) may be rotated about a vertical axis to give horizontal beam direction changes.

4. A target will be placed on the surface of a chalk board, located behing the laser, but the target's position will be determined by the luck of the draw from a set of possible reasonable positions determined by the judges on the day of the competition.

5. The target level will be set at random heights beginning above the level of the laser and the apparatus on the table. Vertical displacement will be handled by the mirror on the end of the meter stick.

6. The front of the laser will be covered while the team completes calculations and adjustments.

C. The Competition

1. Each team of three members may examine the apparatus, declare itself ready to begin, and then draw for their target position and the semi-circular dish angle.

2. Each team must then determine the appropriate angular position for the meter stick and its mirror, and the angle required for the mirror and set both of these prior to releasing the laser beam.

Adjusting the setup by viewing backwards from the target position through the optical system to the laser will not be allowed.

3. Teams will have 5 minutes to complete calculations and adjustments of the mirrors.

4. After the team has set each of the parameters, the beam will be released.

5. Each team should be familiar with index of refraction of water.

6. Teams should bring string, protractor, calculator and other things and help in planning their set-up, as well as notes from advanced planning.

7. The clock on the wall is the official timing device. Students have 5 minutes to examine/touch the apparatus. Following the "draw", students have 5 minutes to set the stick and mirror.

D. Judging and Scoring

1. The judges will monitor all procedures described above. Scores will be awarded based on closest distance on down: 40, 39, 38, 37, etc.

2. First tier scores: If the beam strikes the mirror a measurement will be taken of the radial distance of the beam terminating point from the center of the bulls eye (d) in cm. This will create the first set of terms for ranking.

3. Second tier scores: If the beam misses the mirror at the end of the meter stick, the judges will move the meter stick to allow the mirror to intercept the beam. This score will again be based on closest distance with the high score starting just below the low score of first tier teams.