Question

The radius of a curvature is 20 cm find focal length

Answer 1

focal length = 10 cm

Answer 2

HOLA

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Here , R = 20 cm

$f \: = \frac{r}{2} \\ \\ f \: = \: \frac{20}{2} = \: 10 \\ \\ f \: = \: 10cm$
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HOPE U UNDERSTAND ❤❤❤