A person lives in a high-rise building on the bank of a river 50 m wide. Across the river is a well lit tower of height 40m. when the person, who is at a height of 10 m, looks through a polarizer at an appropriate angle at light of the tower reflecting from the river surface, he notes that intensity of light coming from distance X from his building is the least and this corresponds to the light coming from light bulbs at height ‘Y’ on the tower. (Refractive index of water $\simeq$4/3)