Final answer:
A single laser emits light of a single wavelength, which is monochromatic and coherent, meaning all the photons have the same frequency and phase.
Step-by-step explanation:
The light emitted by a single laser consists of a single wavelength. A laser is a device that produces coherent and monochromatic light. This means that all the photons in the laser light have the same frequency and phase, resulting in a beam of light that is not only very narrow but also very precise in terms of its color (wavelength) and direction. The process of creating laser light involves elevating electrons to different energy levels within a gas. When these electrons return to their ground state, some remain in a metastable state and can be stimulated to release photons in a controlled manner, producing a laser beam with a single, specific wavelength.
Laser technology has numerous applications, especially in the medical field. With the ability to focus laser light to a very small spot and the availability of various types of lasers providing wavelengths from ultraviolet to infrared, one can select a laser wavelength that will be preferentially absorbed by the target material. Objects absorb certain wavelengths of light based on the energy spacing between electron orbitals in their molecules, and this property is used to select the appropriate laser for different uses.