Illusions with transparent glass

 

  
View the video above. You will see three die stacked in a pyramid. All of a sudden a pencil goes right through them as if they weren't there. How can this be?

Explain how this illusion works.

The dice labelled "B" is placed 20 cm from the base of the transparent glass. How far should the red dice be placed from the glass? Explain why.

What type of image is formed in the glass, virtual or real? Explain