Q188 / 225 · JEE Main 2005 · Physics

A thin glass (refractive index 1.5) lens has optical power of $-5 D$ in air. Its optical power in a liquid medium with refractive index $1.6$ will be

  • A
    $1 \mathrm{D}$
  • B
    $-1 \mathrm{D}$
  • C
    $25 \mathrm{D}$
  • Correct answer
    D
    None of these

Solution

$\frac{\mathrm{P}_{\mathrm{m}}}{\mathrm{P}_{\mathrm{air}}}=\frac{\left(\frac{\mu_{\ell}}{\mu_{\mathrm{a}}}-1\right)}{\left(\frac{\mu_{\ell}}{\mu_{\mathrm{m}}}-1\right)}$ $\mathrm{P}_{\mathrm{m}}=5 / 8 \mathrm{D}$

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

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