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Light Reflection and Refraction
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18/08/2021 12:43 pm
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A lens of focal length 20 cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens?
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18/08/2021 12:47 pm
f = 20 cm
m = -10 (Image is real)
u = ?
m = \(\frac{v}{u}\) = -10
v = -10u
\(\frac{1}{v}\) - \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{-10u}\) - \(\frac{1}{u}\) = \(\frac{1}{20}\)
\(\frac{-1 - 10}{10u}\) = \(\frac{1}{20}\)
\(\frac{-11}{10u}\) = \(\frac{1}{20}\)
u = -22 cm
v = -10 x -22 = 220 cm