Changes

The optical lever technique was used to determine the relative amplitude of cantilever vibration at different points along the length. Each cantilever was mounted in the same fashion as before, and the clamp was attached to a ring stand. Also attached to the ring stand was another clamp holding a small speaker. Resonance was achieved by using the speaker to produce a constant sinusoidal output, which traveled through the ring stand to excite the cantilever. A class 111a laser pointer was mounted opposite the free end of the cantilever, pointing towards the fixed end. A white projection screen was mounted above the fixed end of the cantilever. In order to amplify the motion of the cantilever, which is normally very slight, the laser is reflected off the cantilever’s surface, and its own angle of motion is augmented by that of the cantilever relative to the horizontal at the point of reflection.

The optical lever technique was used to determine the relative amplitude of cantilever vibration at different points along the length. Each cantilever was mounted in the same fashion as before, and the clamp was attached to a ring stand. Also attached to the ring stand was another clamp holding a small speaker. Resonance was achieved by using the speaker to produce a constant sinusoidal output, which traveled through the ring stand to excite the cantilever. A class 111a laser pointer was mounted opposite the free end of the cantilever, pointing towards the fixed end. A white projection screen was mounted above the fixed end of the cantilever. In order to amplify the motion of the cantilever, which is normally very slight, the laser is reflected off the cantilever’s surface, and its own angle of motion is augmented by that of the cantilever relative to the horizontal at the point of reflection.

[[File:Laser_Spot.jpg|100px|thumb|right|A laser spot projected onto a screen for recording]]

[[File:Laser_Spot.jpg|150px|thumb|right|A laser spot projected onto a screen for recording]]

To further increase this amplification, a system of mirrors was designed so that the laser would reflect off the cantilever multiple times over the same small lengthwise distance, multiplying the measured change in amplitude by the number of “bounces.” After coming out from the mirror system the laser projects onto the screen, where its sinusoidal motion reflects that of the cantilever. The motion of the laser point (keeping the number of bounces constant) was recorded at 1200 frames per second using a Casio Exilim Pro EX-F1 Digital Camera for each point along the length, moving at approximately one centimeter increments and recording the position of the center mirror relative to the cantilever base.

To further increase this amplification, a system of mirrors was designed so that the laser would reflect off the cantilever multiple times over the same small lengthwise distance, multiplying the measured change in amplitude by the number of “bounces.” After coming out from the mirror system the laser projects onto the screen, where its sinusoidal motion reflects that of the cantilever. The motion of the laser point (keeping the number of bounces constant) was recorded at 1200 frames per second using a Casio Exilim Pro EX-F1 Digital Camera for each point along the length, moving at approximately one centimeter increments and recording the position of the center mirror relative to the cantilever base.