KCET 2025 Physics Paper

To determine the refractive index of a glass slab using a traveling microscope, we have recorded the following data:
Reading for the ink mark on the table surface: 5.123 cm
Reading for the ink mark viewed through the glass slab: 6.123 cm
Reading for chalk dust on top of the glass slab: 8.123 cm
Using these readings, we calculate the refractive index (n) of the glass slab as follows:
The real depth of the glass slab is the difference between the reading for chalk dust on the slab and the reading for the ink mark on the table:
Real depth =8.123‌cm−5.123‌cm=3‌cm
The apparent depth is the difference between the reading for chalk dust on the slab and the reading for the ink mark viewed through the glass slab:
Apparent depth =8.123‌cm−6.123‌cm=2‌cm
The refractive index ( n ) is calculated by dividing the real depth by the apparent depth:
Therefore, the refractive index of the glass slab is 1.5 .