A beam of light is incident on a glass slab. Which of the following measurement is most likely to be correct if the angle of incidence is denoted by $\angle \mathrm{i}$ , the angle of refraction is denoted by $\angle \mathrm{r}$, and the angle of emergence is denoted by $\angle \mathrm{e}$ ?

• When a light beam passes through a glass slab, it bends towards the normal, resulting in a lesser angle of refraction than the angle of incidence. 
• When it emerges through the slab into the air again, it bends away from the normal and becomes parallel to the incoming ray, resulting in the angle of emergence equaling the angle of incidence.

Therefore, the correct measurement would be:  $\angle \mathrm{i} = 30°, \angle \mathrm{r}= 28°, \angle \mathrm{e}= 30°$