Which of the following is a wrong statement?

Which of the following is a wrong statement?
  1. $D=\frac{1}{f}$, where $f$ is the focal length and $D$ is called the refractive power of a lens.
  2. Power is called a clioptre when $f$ is in metres.
  3. Power is called a dioptre and does not depend on the system of unit used to measure $f$.
  4. $D$ is positive for convergent lens and negative for divergent lens.

Solution

The power of a lens is given by the reciprocal of its focal length, $P=\frac{1}{f}$ When $f$ is in metre, then power $P$ is in dioptre. Thus, power depends on the system of unit used to measure $f$. ~

Asked in: MHT CET Full Test 12

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