A glass cube has side length a and its refractive index is `mu = (3)/(2)` . A ray of light (AB) is incident normally on one of its face and after passing through the cube it forms a spot S on screen `sigma`. The cube begins to rotate with angular speed `omega` about its central axis as shown in the Figure. Immediately after the cube begins to rotate, find the speed of the spot S on the screen.
![image](https://learnqa.s3.ap-south-1.amazonaws.com/images/16129527283124956771612952728.png)