5. Which one of the following statements best describes stimulated emission in a laser? a) Electrons collide with atoms in a metastable state and cause photons to be emitted. b) Atoms in a metastable state de-excite and cause electrons to be emitted. c) Photons interact with atoms in a metastable state and cause photons to be emitted. d) Photons interact with atoms in a metastable state and cause electrons to be emitted.
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Answer:
Friction is a force between two surfaces that are sliding, or trying to slide, across each other. ... Friction always works in the direction opposite to the direction in which the object is moving, or trying to move. Friction always slows a moving object down.
(d) Photons interact with atoms in a metastable state and cause electrons to be emitted.
The process by which an incoming photon of a given frequency interacts with an excited atomic electron, causing it to descend to a lower energy level is known as stimulated emission.
In laser action, the stimulating emission sets off a chain reaction in which radiation from one atom stimulates another until all of the system's stimulated atoms have returned to normal. Coherent monochromatic light (light with a single wavelength) is emitted as a result.