Question

When a glass fragment in silicon oil is heated and cooled, which indicates that the refractive index of the glass has been found?

Answer 1

The disappearance of beck lines indicates that the refractive index has been found

Step-by-step explanation:

The Beck Line test is a technnique used in optics. This test heps to determine the refractive index of a material in relation with other material. Basically, it consists in comparing a known refractive index with the unknown refractive index.

The beck line refes to a band formed by the refractive index of both materials, if the band doesn't disappear, it means those materials have differnece index. However, if the band disappears, it means both materials have the same refractive index.

Therefore, the right answer is "the disappearance of beck lines indicates that the refractive index has been found".

Answer 2

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.