Coherence of Laser Light

Definition of Coherent Light
Coherent light refers to light waves that have a fixed phase relationship with one another. This means that the peaks and troughs of the waves are in sync and occur at the same time.

Explanation of Laser Light
Laser light is considered to be coherent because it is produced by a process known as stimulated emission, which causes the atoms in the laser's gain medium to emit photons that are all in phase with one another. These photons then stimulate other atoms to emit more photons in the same phase, creating a cascade effect that results in a beam of light that is highly coherent.

Coordinated Waves of Same Wavelength
Option D, "coordinated waves of same wavelength," is the correct answer because the photons in a laser beam all have the same wavelength and are all in phase with one another. This is what gives laser light its unique properties, such as its ability to travel long distances without spreading out, and its ability to be focused into a very small spot.

Other Options
The other options, such as "divergent beam," "different wavelengths," and "uncoordinated wavelength," are all incorrect because they do not accurately describe laser light. A divergent beam has waves that are not coordinated and are spreading out in different directions. Different wavelengths mean that the light has different colors and is not all in phase with one another. Uncoordinated wavelengths mean that the waves are not in sync with one another and do not have a fixed phase relationship.

Conclusion
In conclusion, laser light is considered to be coherent because it consists of coordinated waves of the same wavelength. This is what allows laser light to have its unique properties and makes it useful in a wide range of applications, from telecommunications to manufacturing.