MCQ
A beaker containing liquid is placed on a table, underneath a microscope which can be moved along a vertical scale. The microscope is focused, through the liquid onto a mark on the table when the reading on the scale is $a$ .
It is next focused on the upper surface of the liquid and the reading is $b$. More liquid is added and the observations are repeated, the corresponding readings are $c$ and $d$. The refractive index of the liquid is
- ✓$\frac{{b - d}}{{d - c - b + a}}$
- B$\frac{{b - d}}{{d - c - b + a}}$
- C$\frac{{d - c - b + a}}{{b - d}}$
- D$\frac{{b - d}}{{a + b - c - d}}$
