The term you are referring to is the focal length, which is the distance between the surface of a reflective surface (such as a mirror) and the focal point.
focal length..
focal length..
The distance between the surface at the center of a reflective surface and its focal point is equal to half the radius of curvature of the surface.
The imaginary line that extends straight out from the center of a reflective surface is the optical axis.
The term that indicates an imaginary line extending straight out from the center of a reflective surface is called the "normal line." This line is perpendicular to the surface at the point of incidence where light strikes the reflective surface. It is essential in understanding the angles of incidence and reflection in optics.
The imaginary line that extends straight out from the center of a reflective surface is the optical axis.
The distance between the listener and the reflecting surface, as well as the reflective properties of the surface, can affect the clarity of an echo. The further the distance and the more absorbent the surface, the less clear the echo will be.
A concave mirror is a spherical mirror with a reflective inside surface. When the reflective surface is made more curved, the distance between the focal point and the surface increases. A concave mirror can form both virtual or real images.
The term that indicates the imaginary line extending straight out from the center of a reflective surface is called the "normal line." This line is perpendicular to the surface at the point of incidence, where a light ray strikes the surface. It is used in optics to analyze the behavior of light as it reflects off surfaces.
The imaginary line that extends straight out from the center of a reflective surface is the optical axis.
When sound waves hit a hard surface, such as a wall or a cliff, they bounce off that surface and return back to the listener's ears. This reflection creates the sensation of hearing the sound again after a slight delay, which is known as an echo. The distance between the source of the sound and the reflective surface, as well as the distance between the surface and the listener, determines the time delay and strength of the echo.