If glass slab is replaced by a hollow slab filled with water, will the net deviation change? For given angle of incidence, will the deviation of the ray in first refraction increase `3s` or decreases compared to the one in glass slab?

Explanation

When glass slab is replaced by a hollow slab filled with water, the net deviation of the ray continues to be zero. The deviation of the ray in first refraction in slab filled with water will become less than deviation of the ray in first refraction in glass slab.
This is because `mu = sin i/sin r`, and `mu_w lt mu_g` therefore, for given `angle i, sin r ` and hence r will be more in water slab. The deviation (i-r) in water slab will less than that in glass slab.