A concave mirror of radius of curvature 40 cm f... - JAMB Physics 2002 Question
A concave mirror of radius of curvature 40 cm forms a real image twice as large as the object.
the object distance is
the object distance is
A
10 cm
B
30 cm
C
40 cm
D
60 cm
correct option: b
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
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
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