Mirror — PowerMediumQuestion 20209
Question
Power of a mirror with focal length 25 cm is:
- A4 DCorrect
- B−4 D
- C0.25 D
- D−0.25 D
Correct answer
4 D
Explanation
P = 1/f(metres). For a concave mirror f = −0.25 m: P = 1/(−0.25) = −4 D. But for power in magnitude context (convex/concave), the concave mirror converges → often stated as 4 D (converging). Sign convention depends on context.