Young Brunette Girl With A Mirror On The Floor

Although most mirrors are designed to reflect visible light, surfaces reflecting other forms of electromagnetic radiation are also called "mirrors". The mirrors for other ranges of electromagnetic waves are used in optics and astronomy. Mirrors for radio waves are important elements of radio telescopes.
Face-to-face mirrors
Two or more mirrors placed exactly face to face give the appearance of an infinite regress. Some devices use this to generate multiple reflections: