Answer: 10 cm (behind mirror).
- A -10 cm (behind mirror)
- B 10 cm (behind mirror)
- C 30 cm in front
- D 60 cm behind mirror
Correct answer: B. 10 cm (behind mirror)
Explanation: 1/v + 1/u = 1/f. 1/v + 1/30 = 1/15. But for convex, f=+15. 1/v = 1/15 - 1/30 = 2/30 - 1/30 = 1/30... Wait, let me redo with proper signs for convex mirror. Convention: f is positive for convex. u=-30. 1/v = 1/f - 1/u = 1/15 - 1/(-30) = 1/15 + 1/30 = 2/30 + 1/30 = 3/30. v=10. Image at 10 cm behind mirror (virtual).
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.