Objects When the concave spherical mirror is located outside the spherical center, the inverted reduced real image is formed, and the image is located between the Focal point and the spherical center. When the object is located between the Focal point and the center of the sphere, the inverted enlarged real image is formed, and the image is located outside the center of the sphere. When the object is located within the Focal point, it stands upright and magnifies the virtual image, as if on the opposite side of the mirror. No image when U=f.

Focus Distance behind the center of the circle in front of the mirror, but not at R/2. However, the incident light is paraxial light, so it can be approximated that the Focus Distance is at R/2.

1/f = 1/d₀ + 1/d_i

f - Focus Distance

d_i - Image distance

d₀ - Object distance