Question
If the distance between object and its two times magnified virtual image produced by a curved mirror is 15 cm , the focal length of the mirror must be:
BITSAT
Physics
Ray Optics
2024
BITSAT 2024 (Memory Based Paper 1)
BITSAT Physics Question (2024) — Solution
Options
- A. 10 3 ~cm
- B. -12 ~cm
- C. -10 ~cm
- D. 15 cm
Answer
C. -10 ~cm
Step-by-step solution
Since, image is magnified. So, it is a concave mirror. m =2= - v u 2= -(15-u) -u 2 u=15-u 3 u =15 u =5 ~cm v =15- u =15-5=10 ~cm Bymirror formula, 1 f = 1 v + 1 u = 1 10 + 1 (-5) = 1-2 10 = -1 10 f =-10 ~cm
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