Where:

• M = magnification
• di = image distance
• do = object distance

Interpretation:

• |M| > 1: Image is larger than object
• |M| < 1: Image is smaller than object
• M > 0: Image is upright
• M < 0: Image is inverted

Where:

• f = focal length
• do = object distance
• di = image distance

Sign Conventions:

• Concave mirror: positive focal length
• Convex mirror: negative focal length
• Real image: positive di (in front of mirror)
• Virtual image: negative di (behind mirror)

Where:

• R = radius of curvature
• f = focal length

Applicable to:

• Spherical mirrors: R = 2f exactly
• Thin lenses: R ≈ 2f (approximate relationship)