The vertical transparent cylinders distort the diagonally placed red pencil behind it:

But the horizontally placed blue pencil seems to double back on itself:

 

Why is this ?

29 minutes ago, Leila Choudhry said:

The vertical transparent cylinders distort the diagonally placed red pencil behind it:

But the horizontally placed blue pencil seems to double back on itself:

 

Why is this ?

Total internal reflection, by the look of it. https://www.bbc.co.uk/bitesize/guides/zctmh39/revision/1