Ray Optics: Refraction — Apparent Shift Complex MCQ

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Refraction — Apparent Shift ComplexHardQuestion 20246

Question

A concave mirror (R = 30 cm) is immersed in a liquid (n = 1.5). Its focal length:

A
15 cm (unchanged)
Correct
B
10 cm
C
22.5 cm
D
30 cm

Correct answer

15 cm (unchanged)

Explanation

Mirror focal length f = R/2 depends only on geometry (angle of incidence = angle of reflection), independent of the medium. Refraction at lens surfaces changes with medium; reflection at mirrors does not. f = 30/2 = 15 cm regardless of medium.

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