Physics307L:People/Ozaksut/Notebook/070912
Speed of Light
Setup
We connected the green Light Emitting Diode (LED light) to a power supply at 200V, and also to the "start" input on the Time to Amplitude Converter (TAC). Then, we connected the Photo Multiplier Tube (light detector) located at the end of a dark tube to reduce ambient light, from the anode to a delay thing and then to the "stop" input on the TAC. The polarizer on the front of the LED lets us maintain a constant amplitude (340mV) of light as we move the LED closer to the detector. We wanted to measure the LED pulse and detected pulse independently first, so we connected the LED directly to the oscilloscope and the detector to the delay and then to the oscilloscope. We kept getting fuzzy signals or weird bumps in the signals, so we added terminators to the end of the cords to try to reduce the resonance. We first had our LED set at 9m from the detector, and when we pushed it in 2m, we noticed the signal from the detector became sharper.
We decided to start from scratch to obtain more precise measurements. This time we pulled the LED to the outer edge of the tube without exposing the PMT to ambient light. We re-polarized the detector until the Oscillioscope showed a maximum amplitude of 100mV.
