Roger Rothenberg
holograms

Using the LitiHolo Holography Kit (http://www.litiholo.com/hologram_kits.htm), I created transmission holograms and attempted to create a reflection hologram.

Transmission Hologram Procedure:
In the dark room, I assembled the LitiHolo kit as instructed (see image 1), with the object to be rendered in the delineated box on the black plastic base (with rubber foundation to reduce vibration). I turned on the laser, turned off all other light in the darkroom (save for a blue darkroom LED [the LED’s blue wavelength, while illuminating the room enough for me to get around, did not affect the hologram, which was produced by red light]), and used white paper to ensure that the laser spread to the whole surface of the spot I would place the photosensitive glass. I used a black cardboard “shutter” to block the laser’s path to the object so that I could position the photo glass without exposure. After waiting one minute for the setup to settle (LitiHolo instructions recommend three minutes for a clearer hologram), I removed the shutter. After waiting approximately five minutes (as recommended by LitiHolo), I removed the object and made sure the hologram had been recorded. At this point it was safe to turn the light back on, as the hologram was finished and would not be exposed further. See image 3 for an example transmission hologram.

Reflection Hologram Procedure:
There were no instructions on creating a reflection hologram from the LitiHolo kit, but I attempted to create my own setup (see image 2) based on more detailed procedures for reflection holograms. Other sets of instructions recommended a greater distance between laser and recording glass, so I increased the spacing between the laser mount and object base provided by LitiHolo. I rotated the base so that the slot for the photo glass was between laser and object. From this point, I proceeded as I did with the transmission hologram. After getting some unremarkable results, I tried again, this time with an additional non-photo glass placed behind the object, with the rationale that this might increase the amount of light scattered from the object onto the photo glass. This did produce a more visible reflection hologram.

Though the above procedures did result in visible holograms, several factors might have improved their quality:

• Decreasing ambient vibrations would have made for a sharper, more precise holographic image. While this might be difficult in the school’s darkroom, some kind of shock-absorbing foundation beneath the setup (such as sand) might help
• Further fine-tuning of the laser’s path of illumination would have made for more centered holograms. Many of those I created had blank space below or around the hologram, indicating unused parts of the photo glass
• Additional mirrors may have allowed for a more controlled setup of the direction of the interfering beams. LitiHolo did not provide additional mirrors
• A more powerful laser might have allowed for a decreased exposure time, which in turn would create a shorter window for vibrations to disrupt the image

Image 1: Transmission Hologram Setup

Image 2: Reflection Hologram Setup

Image 3: Example Transmission Hologram of Car Figurine With Hood Open

For our project, we will be examining a possible relationship between the energy used by a cellular phone and the radiation that it emits while in use. To gather our data, we will be using Watts Up Pro and an RF meter to measure the microwave radiation generated by electric currents within the phone. In order to obtain a statistically significant sample, we will be testing roughly ten to fifteen phones of different models. This will also allow us to see if a phone’s make and model are related to the amount of radiation it emits. The testing will take place in the Retreat on Tuesday, November 15, at 3 pm. This data will be gathered as a group, and we will then split up the remaining work amongst ourselves. For example, I will be responsible to creating the chart and graph to display our findings, while Ali will handle a visual graphic comparing types of phones, and Sam will present our results and conclusions. Our expected outcome is that the more energy that a phone uses, the more radiation it will emit.

Background:

Compact discs have permanently changed the way people listen to, store and record music. Though the uses for them have expanded since their initial release in the late 1970’s and their popularity has declined considerably since the invention of the mp3 and related music players, they are solely responsible for the digital music revolution. Analogue music recorded on vinyl records had its own advantages and disadvantages. Of the most concern here is a portability and shock resistance issue that simply could not be overcome due to the method of encoding and reading used to store the audio information on records. Compact disks overcame both of these issues, though the differences in data storing allowed for new approaches to mixing and mastering recordings. These mixing and mastering trends in turn have changed people’s preferences for recording style. People have come to expect certain qualities from the audio they listen to, qualities which often were not present on recordings made decades ago. Thus, when songs are rereleased, they are often remastered to cater to more current acoustic preferences.

Due to the physical limitations of needle vibration within the grooves of the record, an inherent volume limit to recordings was imposed on records. However, even during the days of turntables, louder recordings tended to attract more attention in situations where sound quality was not as apparent (radio/ jukeboxes). Thus, recording studios would make their recordings as loud as possible in much the same way that television stations tend to make the commercials louder than the actual program. People have a tendency to equate louder music with higher quality recordings (a tendency supported by our testing. Many of our subjects stated that one side sounded better simply because it was “louder”). Upon the introduction of the compact disk, this physical limitation was removed allowing for much louder music. The change wasn’t immediate. It took many years.

Rather than merely upping the volume of the entire track, a practice called compression is often used. Compression takes the quietest sounds and makes them louder while softening the louder sounds. Because it is easier to more clearly discern louder sounds, people will often equate better sound quality with a song that has less dynamic range. You can more easily hear softer sections of music in a more compressed track. Ironically, compact disks were marketed for their potential for greater dynamic range (complete silence could be achieved as no needle noise is involved). However, such changes to audio after it is recorded can cause distortions or clipping. The most drastic changes to audio compression trends occurred between 1990 and 2000.

We set out to test whether the volume itself was the source of perceived increase in musical recording quality over the years, or if the clipping and distortion caused a significant decrease in perceived quality when volume was adjusted for.

Continue reading →