Monthly Archives: June 2014

Lasers! Lasers! Lasers!

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Lets learn about lasers!

Key Terms:
Lasing Medium / Gain Medium – The material which forms the laser light.
Pump – The energy source needed to induce the population inversion.
Population Inversion – The act of causing the electrons in the lasing medium to jump to higher energy states.
Meta-Stable – A short period of stability.
Stimulated Emission – When an electron drops to a ground state and emits a photon as a result of another photon passing by it. Both photons are coherent.
Spontaneous Emission – When an electron drops to a ground state and emits a photon after a short time in a meta stable state.

The lasers in the video are DPSS Lasers (Diode Pumped Solid State)

An Infrared Aluminum Gallium Arsenide diode laser emits 808nm photons. These pump a Neodymium-Doped Yttrium Orthovanadate or Neodymium-Doped YAG crystal which emits 1064nm laser light. This light is Freq doubled using Potassium Titanyl Phosphate crystal to become 532nm, a beautiful green color


Simple Decay Equation – Example (Polonium 210)

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How to calculate the current activity of a source given the activity at one point, the time which has elapsed, and the decay constant.

Activity_now = Activity_then * e^-((ln2/halflife)*elapsed_time)

Now, enter into your calculator for activity of 1000Bq, halflife of 20min, and elapsed time of 40min:

1000 * e ^ – ( ( ln(2) / 20 ) * 40 ) )