An object is placed in front of a concave mirror whose radius of curvature is 12cm. If the magnification of the Image produced is 1.5, how far is the object from the mirror?
8cm
10cm
15cm
18cm
20cm
Correct answer is B
Radius of curvature(r)=12cm
focal length(F) = r ÷ 2 → 12 ÷ 2 = 6cm
therefore F = 6cm
magnification(M) = v ÷ u
1.5 = v ÷ u
:v = 1.5u
Using mirror formula
1/f =1/v + 1/u
\(\frac{1}{6}\) =\(\frac{1}{1.5u}\) + \(\frac{1}{u}\)
\(\frac{1}{6}\) = \(\frac{1 + 1.5}{1.5u}\)
\(\frac{1}{6}\) = \(\frac{2.5}{1.5u}\)
1 * 1.5u = 2.5 * 6
u = \(\frac{15}{1.5}\) = 10
therefore object distance =10cm.