Answer: infinite.
- A infinite
- B zero
- C equal to its length
- D 25 cm
Correct answer: A. infinite
Explanation: A plane mirror has an infinite radius of curvature, so its focal length f = R/2 is infinite.
Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.
Concept context
Reflection, refraction, lenses, mirrors, total internal reflection.