<span>When a glass fragment in silicon oil is heated and cooled, the refractive index of the glass has been found when both the becke lines and the glass will disappear. As the oil refractive index changes in the process of heating so that it equals the glass refractive index, the fragment edges fade.</span>
Answer:
Density = Mass / Volume
Mass = .3 kg
Volume = 2 * 5 * 4 = 40 m^3
Density = .3 g / 40 m^3 = .0075 kg / m^3
1 kg/m^3 = kg * 1000 g / kg / (1 m^3 * (100 cm/m)^3) = 10E-3 gm/cm^3
Density = 7.5 E-3 gm/cm^3