The correct answer is option 2: coherent light.

A laser is a device that produces a narrow, intense beam of light, which is known as laser light. This light is different from ordinary light sources, such as light bulbs, because it is coherent. Coherence refers to the property of light waves being in phase with each other. In other words, all the waves of laser light have the same frequency and are aligned with each other. This makes the laser light highly focused and concentrated.

Option 1, a beam of white light, is incorrect because lasers do not produce white light. White light consists of a combination of different colors and frequencies, whereas laser light is of a single frequency.

Option 3, microwaves, is incorrect because microwaves are a different form of electromagnetic radiation that is used for communication and heating.

Option 4, X-rays, is incorrect because X-rays are also a different form of electromagnetic radiation that is used for imaging and medical purposes.

Therefore, the correct answer is option 2: coherent light.