Q134 / 180 · COMEDK 2017 · Physics

Which of the following is a wrong statement?

  • A
    $D=\frac{1}{f}$, where $f$ is the focal length and $D$ is called the refractive power of a lens.
  • B
    Power is called a clioptre when $f$ is in metres.
  • Correct answer
    C
    Power is called a dioptre and does not depend on the system of unit used to measure $f$.
  • D
    $D$ 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 $f$.

Hence, the correct answer is option: 'C'.

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