Question

What happens when a ray of light strikes a glass slab at 90 degrees?

Answer 1

it will always be equal 

Answer 2

Hello freind !! when a ray of light strikes a glass slab at 90 * the following thing can happen

●The ray of light falls normally(at 90) on the glass slab, thus the ray passes straight through.
●Thus, angle of incidence =0
          angle of refraction=0 
means both will zero
hope this helps you:)