Question

Which of the following is a unique property of a laser.
A. directional
B. speed
C. coherence
D. wavelength

Answer 1

A laser is a device that produces light via an optical amplification process based on the stimulated emission of electromagnetic energy. "Light amplification by stimulated emission of radiation" is an abbreviation for "laser." Theodore H. Maiman of Hughes Research Laboratories constructed the first laser in 1960, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.

Complete answer:
A laser differs from other light sources in that it emits coherent light. Laser cutting and lithography are made possible by spatial coherence, which allows a laser to be focussed to a small area. Spatial coherence also enables laser pointers and lidar by allowing a laser beam to remain narrow across long distances (collimation). High temporal coherence allows lasers to generate light with an extremely narrow spectrum. Alternatively, temporal coherence may be utilised to create ultrashort light pulses with a broad spectrum but femtosecond durations.

One of the distinctive features of laser light is coherence. It results from the amplification provided by the stimulated emission mechanism. Because the emission events that give the amplified light are triggered by a similar stimulus, the released photons are "in step" and have a clear phase relationship. This coherence may be characterised in terms of temporal and spatial coherence, both of which are crucial in creating the interference that makes holograms possible.

Coherence is a necessary characteristic for laser beams because wave trains of the same frequency are in phase. Extremely high power results from high coherence. Coherence is one of the distinguishing characteristics of laser light. It is the outcome of the stimulated emission mechanism's amplification. The emitted photons are in step and have a clear phase connection because the emission events that create the enhanced light are caused by a comparable stimulus.

Therefore, option C is correct.

Note: Two wave sources are said to be coherent in physics if their frequency and waveform are the same. Coherence is a wave characteristic that allows for stationary (i.e. constant temporally and spatially) interference. It has become a highly significant term in quantum physics since it comprises multiple separate ideas, which are limiting situations that never exactly exist in reality but provide an understanding of the mechanics of waves.Coherence, in a broader sense, refers to the qualities of the correlation between physical parameters in a single wave, as well as between several waves or wave packets.