Question

What is the focal length of lens if power of lens is -0.5D

Answer 1

P = 1/f
Thus focal length will be = 1/0.5 = - 2 metre

Answer 2

$\: \: \: \: \: \: \: P = \frac{1}{f(in \: \: \: m)} \\ = > ( - 0.5) = \frac{1}{f} \\ = > f = \frac{ - 1}{0.5} = \frac{ - 1}{ \frac{1}{2} } = ( - 2)m.$




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