A transparent glass slab of thickness t=0.50 ~cm is placed with its face A B on a horizontal table. A hemispherical water drop of radius R=0.33 ~cm condenses on the glass slab as shown in figure. The refractive indices of the slab and the water drop are respectively 1.50 and 1.33 . The image of the object at 0 on the face A B is viewed after refraction from the drop. Taking O E Q as the optical axis, the distance ( c