Q174 / 180 · KCET 2025 · Physics

In determining the refractive index of a glass slab using a travelling microscope, the following readings are tabulated (a) Reading of travelling microscope for ink mark $=5.123 \mathrm{~cm}$ (b) Reading of travelling microscope for ink mark through glass slab $=6.123 \mathrm{~cm}$ (c) Reading of travelling microscope for chalk dust on glass slab $=8.123 \mathrm{~cm}$ From the data, the refractive index of a glass slab is

  • Correct answer
    A
    1.500
  • B
    1.601
  • C
    1.399
  • D
    1.390

Solution

$\begin{aligned} & \text { Real depth }=(8.123-5.123)=3 \mathrm{~cm} \\ & \text { Apparent depth }=8.123-6.123=2 \mathrm{~cm} \\ & \mathrm{n}=\frac{\text { R.D }}{\text { A.D }}=1.5\end{aligned}$

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

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