It should bend upwards , because if we move upwards then refractive index increases and thus the rays will tend to turn towards normal (think like a near horizontal incident ray is incident from lower surface to the air surface about that level )
Sir how do we know by huygens principle that it will bend upwards?? Like isn't the answer more to do with refractive index and it's variation with height than this principle?? Has this question deliberately been made more confusing?
Basically snells law can be derived from huygens principle and hence we can say that this phenomenon can be explained through huygens principle , altough that statement was not required, but still maybe it was there to confuse students