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Light Reflection and Refraction
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13/08/2021 2:01 pm
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(a) Draw a diagram to represent a convex mirror. On this diagram mark principal axis, principal focus F and the centre of curvature C if the focal length of convex mirror is 3 cm.
(b) An object 1 cm tall is placed 30 cm in front of a convex mirror of focal length 20 cm. Find the size and position of the image formed by the convex mirror.
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13/08/2021 2:04 pm
(a) figure.png
(b) \(h_1\) = 1 cm, u = -30 cm, f = 20 cm, \(h_2\) = ?, v = ?
\(\frac{1}{v}\) + \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{v}\) + \(\frac{1}{-30}\) = \(\frac{1}{20}\)
\(\frac{1}{v}\) = \(\frac{1}{30}\) + \(\frac{1}{20}\)
v = 12 cm
The image is formed 12 cm behind the mirror.
m = -\(\frac{v}{u}\) = \(\frac{h_2}{h_1}\)
m = -\(\frac{12}{-30}\) = \(\frac{h_2}{1}\)
\(h_2\) = 0.4 cm