PHYSICS

JAMB 2002 - Question 28

Physics 2002 JAMB Past Questions - Question 28: A concave mirror of radius of curvature 40cm forms a real image twice as large as the object.. The object distance is

Choose the correct answers from the options given.
A concave mirror of radius of curvature 40cm forms a real image twice as large as the object.. The object distance is
A:
B:
C:
D:
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Correct Answer

A

Explanation

if r = 40 cm , then f = r/2 = 40/2 = 20 cm
then for a real image by a concave mirror,
magnification M = f/u-f => 2 = 20/U-20
therefore 2(u-20) = 20
2u - 40 = 20
2u = 40 + 20
2u = 60/2 = 30 cm