What characteristic describes laser beams as monochromatic?

Laser beams are characterized as monochromatic because they emit light at a single, specific wavelength. This means that the light produced by a laser is made up of one consistent color rather than a mix of different wavelengths or colors. Monochromatic light is particularly important in applications such as spectroscopy and holography, where the uniformity of wavelength enhances the precision and quality of the results.

In contrast, varying wavelengths, multiple colors, and sharp edges do not accurately describe the concept of monochromatic light. Varying wavelengths would indicate a spectrum of colors, and multiple colors would also imply the presence of different wavelengths. Sharp edges refer to the spatial profile of the laser beam but do not contribute to the definition of monochromatic light. Therefore, the defining characteristic of a monochromatic laser beam is its emission of light at a single wavelength, making the second choice the correct one.