A student noted the thickness of glass sheet using a screw guage. on this main scale it reads 3 divisions while 8 division on the circular scale concides with index line its thickness is?

The thickness of the glass sheet can be calculated using the screw gauge reading, where 1 main scale division corresponds to 0.5 mm and 50 equal circular scale divisions make one complete turn. In this case, the thickness would be (3 \times 0.5 + \frac{8}{50} \times 0.5) mm.