When a laser beam is fired toward a mirror, not all of the original electromagnetic energy is reflected. Some of the energy is indeed lost in the process. The amount of energy that is reflected and the amount that is lost depend on several factors, including the properties of the mirror and the incident angle of the laser beam.
Reflectivity: The reflectivity of a mirror is a measure of how effectively it reflects incoming light. Mirrors typically have high reflectivity, especially for specific wavelengths or a narrow range of frequencies. However, even with high reflectivity, there is always some loss of energy during reflection due to imperfections in the mirror's surface, absorption, scattering, or other factors.
Incident Angle: The angle at which the laser beam strikes the mirror, known as the incident angle, also plays a role in the amount of energy that is reflected. The angle of incidence affects the efficiency of reflection, with the highest reflection occurring when the angle of incidence is equal to the angle of reflection (known as the specular reflection).
Mirror Quality: The quality of the mirror surface is crucial in minimizing energy losses. High-quality mirrors are designed to have low surface roughness and high reflectivity over a broad range of incident angles, minimizing energy loss due to scattering or absorption.
Mirror Coatings: Many mirrors have thin coatings, such as metallic or dielectric layers, to enhance their reflectivity and minimize energy loss. These coatings are designed to optimize reflectivity for specific wavelengths or a range of frequencies.
Despite efforts to maximize reflectivity, there is always some energy loss during reflection. The actual amount of energy loss depends on the specific mirror's characteristics and the incident conditions. However, high-quality mirrors can achieve very high reflectivity, often exceeding 99% for specific wavelengths or frequency ranges.
It's important to note that even a highly reflective mirror may absorb a small fraction of the incident energy, especially if the incident angle deviates significantly from the ideal angle of reflection. Additionally, mirrors can also undergo other phenomena like scattering or diffraction, which may further contribute to energy loss.