March 01, 2007

Science Can Be Fun

Laser light displayBeen busy for a few days. Now almost through with all my assignments.
I worked and fixed some critical EKG/EEG issue to some extent. But the superimposing (background) noise is really bugging the contraption. I put the device within a metal enclosure, used good quality coaxial cable, yet the device seems prone to catch the 50 Hz hum, and the noise from the SMPS (Switched Mode Power Supply) of the computer. I used the scope software to analyze the input and interface it to the computer, so that my computer monitor could behave as a stand alone oscilloscope. I used the 'mic in' jack of the computer for signal input. For power, I used two 9 volt general purpose batteries, to ensure safety and also to eliminate mains hum. Perhaps, they need to be screened further. I'll look into this.

Next I did a kind of magic with a laser pointer! It was a hit among kids and adults alike. All I did was that I got hold of a class 3A, 630-680 nM key chain laser (the light is red at this electromagnetic wavelength), which sells for about 60-70 cents here in Calcutta. I tied one end (the key side) of the laser to the spindle/axle of a DC motor, via a spring. I tied a rubber band across the push button switch of the laser, so that it was constantly on. Then I switched on the 12 V supply of the motor. As the laser pointer rotated, the centrifugal force stretched the spring which increased in length gradually (as per 'Young's modulus') as the motor gathered speed. The resulting beam gave a vivid and bright spiral trajectory on the wall. The persistence of vision gave an added effect. I observed all the necessary precautions needed with lasers, of course!

Then I did a few basic things with polarizers as my young science fans wouldn't let me go. You would be surprised to know that I actually got these little things from my old mobile phone.a demonstration of the wave nature of light using polarizers collected from used mobile phone LCD display I found out two remarkable pieces of polarizers in the LCD panel portion (picture on the left). I showed them what they were and the peculiar way they behaved. The color changed as one was rotated with respect to the other. You can watch a medium quality video here (754KB, WMV format). The experiment demonstrates the wave nature of light. Needless to say, they were amused.

Finally, I feel tempted here to mention about mobile flashers, those tiny devices, which flash as one uses the cell phone, without any wiry connections. More about them later, may be in my other blog.
Post a Comment