Why, second time around?

Because after being broken, the small pieces are not in the same plane, which is equivalent to countless small mirrors and become many mirror images.

Together, it looks the same as the original, but there are still subtle differences, such as the three pieces can not be completely on the same plane and the edges are irregular. If they are not on the same plane, they will be imaged separately, which is equivalent to multiple mirrors. If you use a mirror that has been precisely cut and then put it together completely on a horizontal plane, the result should be exactly the same as the mirror.

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The mirror's reflection of light obeys the law of reflection, and its reflection ability depends on the angle of incident light, the smoothness of the mirror and the properties of the plated metal film. The imaginary line perpendicular to the mirror is called the normal, and the angle between the incident light and the normal is equal to the angle between the reflected light and the normal. The object in front of the plane mirror becomes an upright virtual image behind the mirror, and the distance from the virtual image to the mirror surface is equal to the distance from the object to the mirror surface.

If you want to see my whole length in the mirror, the mirror must be at least half my length, because the incident angle is equal to the reflection angle. The reflective surface of concave mirror faces the center of curvature.