JAMB - Physics (2002 - No. 20)
a ray of light which strikes a glass slab from air at normal incidence passes through the slab
undeviated and undisplaced at a lower speed
deviated and undisplaced at a lower speed
deviated and displaced at a lower speed
undeviated and displaced at a faster speed
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The angle of refraction will be zero as the angle of incidence is zero in this case. This is a rule, that whenever a ray strikes perpendicularly or normally to a surface, no refraction will take place and hence the ray will pass through without deviating from its path.