LASER light is the result of
Correct answer: D. Stimulated emission
- A. Spontaneous emission
- B. Ordinary emission
- C. Absorption of radiation
- D. Stimulated emission
Explanation
Laser stands for Light Amplification by Stimulated Emission of Radiation. Laser light utilizes stimulated emission. Stimulated emission requires the presence of a photon. An "incoming" photon stimulates a molecule in an excited state to decay to the ground state by emitting a photon. The stimulated photons travel in the same direction as the incoming photon. As a result a coherent, monochromatic and intense beam of laser light is created. For stimulated emission to be the dominant process, the excited state population must be larger than the lower state population. This is achieved by excitation of the lasing atoms or molecules - this is called PUMPING.
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About Quantum Theory and Radiation
Quantum theory treats electromagnetic radiation as packets of energy called photons, with energy proportional to frequency through E equals hf. The topic covers Planck's hypothesis, photon momentum, the photoelectric effect, threshold frequency, work function and wave particle duality, distinguishing quantised energy exchange from classical continuous radiation.
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