A fully reflective mirror is an optical element used to achieve complete reflection of light. In an ideal situation, a fully reflective mirror can achieve the reflection of light, that is, all incident light is reflected without transmitted light. This is because the working principle of full reflection mirrors is based on the phenomenon of total reflection when the incident angle of light from a dense medium to a sparse medium is greater than the critical angle.
However, in reality, full reflection mirrors may have some energy loss, which may be caused by the material's light absorption, imperfect surface reflectivity, or other optical loss factors. Therefore, although full reflection mirrors can theoretically achieve reflection, there may be some energy loss in practical applications.
To ensure a greater degree of total reflection, some measures can be taken, such as selecting high-quality full reflection materials, optimizing mirror surface treatment, and reducing the angle of light incidence. These measures can improve the reflection efficiency of the full reflection mirror and minimize energy loss as much as possible.
In summary, although a total reflection mirror can achieve complete reflection in theory, there may be some energy loss in practical applications, so we usually refer to it as "almost total reflection" rather than total reflection.