The focal length of a concave mirror is 15 cm. The radius of curvature is
A. 45 cm
B. 15 cm
C. 30 cm
D. 7.5 cm
Answer: Option C
Solution (By JKSSB Mock Tests)
For spherical mirrors, R = 2f. So R = 2 × 15 = 30 cm. Sign convention: for concave mirror, f and R are negative by Cartesian convention, but magnitude 30 cm. So 30 cm is correct.
Explanation:
Atomic number Z = number of protons. Defines chemical element. Mass number = protons + neutrons. Isotopes same Z, different neutrons. Isobars same A, different Z.
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