Michelson interferometer is an instrument used to measure

Explanation

The Michelson interferometer is a device that splits a beam of light into two paths, reflects them back, and then recombines them to create an interference pattern. This pattern is highly sensitive to changes in path length, which is directly related to the wavelength of light. By analyzing these patterns, the instrument can accurately measure the wavelength. The other options, such as frequency, intensity, and amplitude, are not the primary focus of measurement for this interferometer. Frequency is typically determined by the source of light, intensity is a measure of power per unit area, and amplitude is related to the energy of the wave, none of which are the primary measurements made by this device.