A glass cube of refractive index $$1.5$$ and edge $$1\ \text{cm}$$ has a tiny black spot at its center. A circular dark sheet is to be kept symmetrically on the top surface so that the central spot is not visible from the top. Minimum radius of the circular sheet should be. Given $$\frac{1}{\sqrt2}=0.707$$, $$\frac{1}{\sqrt3}=0.577$$, $$\frac{1}{\sqrt5}=0.447$$

A

$$0.994\ \text{cm}$$

B

$$0.447\ \text{cm}$$

C

$$0.553\ \text{cm}$$

D

$$0.577\ \text{cm}$$