I would like to try to measure the speed of light, for a high school science fair project. I have no experience with lasers.
The experiment I envision would shoot a small, square-wave-modulated laser through a beam splitter. One portion of the light would be sent directly to a photo detector. The other beam would travel a longer path (probably 5 to 20 meters,) and be directed back onto the same photo detector. The response of the photo detector would be observed with an oscilloscope. If all goes well, I imagine a waveform showing two overlapping pulses, which could be independently removed by blocking each beam. Measuring the overlap would allow calculating the speed of light.
My budget for this is very low. I am looking for recommendations for:
1 - A modulated laser source. Are cheap laser pointers modulated? Do I need to get a laser diode, and drive it with my own circuit?
2 - Would the laser require eye protection? I'm interested it the lowest power that would do the job, mostly for budget reasons.
3 - A photo detector. I am guessing I need a photodiode with a pretty fast response time.
Any advice would be welcome, especially specific part numbers, and sources for purchase.
Did I mention that my budget is low?
Thanks for reading this far,
Kwak
The experiment I envision would shoot a small, square-wave-modulated laser through a beam splitter. One portion of the light would be sent directly to a photo detector. The other beam would travel a longer path (probably 5 to 20 meters,) and be directed back onto the same photo detector. The response of the photo detector would be observed with an oscilloscope. If all goes well, I imagine a waveform showing two overlapping pulses, which could be independently removed by blocking each beam. Measuring the overlap would allow calculating the speed of light.
My budget for this is very low. I am looking for recommendations for:
1 - A modulated laser source. Are cheap laser pointers modulated? Do I need to get a laser diode, and drive it with my own circuit?
2 - Would the laser require eye protection? I'm interested it the lowest power that would do the job, mostly for budget reasons.
3 - A photo detector. I am guessing I need a photodiode with a pretty fast response time.
Any advice would be welcome, especially specific part numbers, and sources for purchase.
Did I mention that my budget is low?
Thanks for reading this far,
Kwak